[Federal Register Volume 76, Number 183 (Wednesday, September 21, 2011)]
[Proposed Rules]
[Pages 58650-58680]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-24048]



[[Page 58649]]

Vol. 76

Wednesday,

No. 183

September 21, 2011

Part III





Department of the Interior





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Fish and Wildlife Service





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50 CFR Part 17





 Endangered and Threatened Wildlife and Plants; 12-Month Finding on a 
Petition To List Van Rossem's Gull-Billed Tern as Endangered or 
Threatened; Proposed Rule

  Federal Register / Vol. 76 , No. 183 / Wednesday, September 21, 2011 
/ Proposed Rules  

[[Page 58650]]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R8-ES-2010-0035; MO 92210-0-0008-B2]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition To List Van Rossem's Gull-billed Tern as Endangered or 
Threatened

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service, announce a 12-month 
finding on a petition to list van Rossem's gull-billed tern 
(Gelochelidon nilotica vanrossemi) as endangered or threatened and to 
designate critical habitat under the Endangered Species Act of 1973, as 
amended (Act). After review of the best available scientific and 
commercial information, we find that listing van Rossem's gull-billed 
tern is not warranted at this time. However, we ask the public to 
submit to us any new information that becomes available concerning the 
threats to van Rossem's gull-billed tern or its habitat at any time.

DATES: The finding announced in this document was made on September 21, 
2011.

ADDRESSES: This finding is available on the Internet at http://www.regulations.gov at Docket Number FWS-R8-ES-2010-0035. Supporting 
documentation we used in preparing this finding is available for public 
inspection, by appointment, during normal business hours at the U.S. 
Fish and Wildlife Service, Carlsbad Fish and Wildlife Office, 6010 
Hidden Valley Road, Suite 101, Carlsbad, California 92011. Please 
submit any new information, materials, comments, or questions 
concerning this finding to the above street address.

FOR FURTHER INFORMATION CONTACT: Jim Bartel, Field Supervisor, Carlsbad 
Fish and Wildlife Office, 6010 Hidden Valley Road, Suite 101, Carlsbad, 
California 92011; by telephone at 760-431-9440; or by facsimile to 760-
431-9624. If you use a telecommunications device for the deaf (TDD), 
you may call the Federal Information Relay Service (FIRS) at 800-877-
8339.

SUPPLEMENTARY INFORMATION:

Background

    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (Act) (16 U.S.C. 1531 et seq.) requires that, for any petition 
to revise the Federal Lists of Endangered and Threatened Species that 
contains substantial scientific or commercial information that listing 
the species may be warranted, we make a finding within 12 months of the 
date of receipt of the petition. In this finding, we will determine 
that the petitioned action is: (1) Not warranted, (2) warranted, or (3) 
warranted, but the immediate proposal of a regulation implementing the 
petitioned action is precluded by other pending proposals to determine 
whether species are endangered or threatened, and expeditious progress 
is being made to add or remove qualified species from the Federal Lists 
of Endangered and Threatened Species. Section 4(b)(3)(C) of the Act 
requires that we treat a petition for which the requested action is 
found to be warranted but precluded as though resubmitted on the date 
of such finding, that is, requiring a subsequent finding to be made 
within 12 months. We must publish these 12-month findings in the 
Federal Register.

Previous Federal Actions

    In our November 15, 1994, Candidate Notice of Review (59 FR 58982), 
we included van Rossem's gull-billed tern as a Category 2 candidate. 
Category 2 taxa were defined as those taxa for which information in the 
possession of the Service, at that time, indicated that proposing to 
list as endangered or threatened was possibly appropriate but for which 
persuasive data on biological vulnerability and threats were not 
available to support proposed rules. In our February 28, 1996, 
Candidate Notice of Review (61 FR 7596), we announced our decision to 
discontinue recognition of Category 2 candidates, including van 
Rossem's gull-billed tern. This decision was finalized on December 5, 
1996 (61 FR 64481). Since that time, van Rossem's gull-billed tern has 
not been treated as a candidate for Federal listing under the Act.
    On June 8, 2009, we received a petition from the Center for 
Biological Diversity dated June 3, 2009, requesting that we list the 
``western'' or ``van Rossem's'' subspecies of gull-billed tern 
(Gelochelidon nilotica vanrossemi) as endangered or threatened under 
the Act, and that we designate critical habitat concurrent with listing 
(CBD 2009, pp. 1-40). Included in the petition was supporting 
information regarding the subspecies' taxonomy, ecology, distribution, 
status, and potential threats. Although not expressly stated in the 
petition, we assumed the petition was a request to list van Rossem's 
gull-billed tern as endangered or threatened throughout the subspecies' 
entire range.
    In response to the Center for Biological Diversity's June 3, 2009, 
petition to list van Rossem's gull-billed tern as endangered or 
threatened throughout its range, we sent a letter to Center for 
Biological Diversity, dated August 18, 2009, acknowledging receipt of 
the petition and informing the petitioner that we concluded the 
petition did not indicate that an emergency situation existed for this 
subspecies and that emergency listing was not warranted. We also stated 
that we were addressing a significant number of listing and critical 
habitat actions in Fiscal Year 2009 (October 1, 2008, through September 
30, 2009) pursuant to court orders, judicially approved settlement 
agreements, or other statutory deadlines; however, we noted that we had 
secured funding to begin reviewing the petition in that fiscal year. 
Further, we said we anticipated publishing our 90-day finding in Fiscal 
Year 2010.
    We published our 90-day finding on the petition to list van 
Rossem's gull-billed tern as endangered or threatened in the Federal 
Register on June 9, 2010 (75 FR 32728). In that finding we determined 
that the petition presented substantial scientific or commercial 
information, per section 4(b)(3)(A) of the Act, indicating that listing 
the van Rossem's gull-billed tern throughout its range may be 
warranted. The current notice constitutes the 12-month finding on the 
June 3, 2009, petition to list the van Rossem's gull-billed tern 
throughout its range as endangered or threatened under the Act.

Species Information

Species Description and Taxonomy
    Van Rossem's gull-billed tern (Gelochelidon nilotica vanrossemi) is 
medium-sized compared to other tern species (Parnell et al. 1995, p. 
2). Like most tern species, its plumage is generally pale gray above 
(dorsally), white below (ventrally), with breeding (alternate) plumage 
adults having black on the top of the head (Parnell et al. 1995, p. 2). 
Gull-billed terns, including van Rossem's gull-billed tern, differ from 
other species of terns by having a proportionately stouter bill that is 
black throughout the year (Bent 1921, p. 201; Parnell et al. 1995, p. 
2; Pyle 2008, p. 706). Gull-billed terns are powerful flyers, and 
despite appearing heavier bodied than most tern species, they exhibit a 
buoyant agility, especially while foraging (Audubon 1840, p. 1; Bent 
1921, p. 201; Molina and Marschalek 2003, p. 3).

[[Page 58651]]

    Van Rossem's gull-billed tern is a seabird in the avian order 
Charadriiformes (shorebirds, gulls and terns, auks, and allies) and 
family Laridae (skuas, gulls, terns, and skimmers) (AOU 1998, pp. 141 
and 181), although terns are sometimes considered a separate family, 
Sternidae (e.g., Ridgeway 1919, p. 458; Gochfeld and Burger 1996, pp. 
572 and 624; Ericson et al. 2003, pp. 1-14).
    Gelochelidon is a monotypic genus (a genus with only one species, 
Gelochelidon nilotica, the gull-billed tern). Gelochelidon has 
historically been placed in synonymy with Sterna (e.g., Saunders 1876, 
p. 644). However, a more recent analysis using mitochondrial DNA and 
morphological features concluded that the gull-billed tern is 
sufficiently differentiated from other tern species to resurrect 
Gelochelidon as a genus separate from Sterna (Bridge et al. 2005, pp. 
459-469; see also Banks et al. 2006, p. 930).
    The gull-billed tern (the species as a whole) has a worldwide 
distribution, albeit discontinuous, and may comprise up to six 
subspecies (Parnell et al. 1995, p. 3; Gochfeld and Burger 1996, p. 
645). Of those, two subspecies are described in North America (Molina 
2008, p. 188), with Gelochelidon nilotica aranea breeding along the 
Atlantic and Gulf of Mexico coasts of the United States and 
northeastern Mexico, and with G. n. vanrossemi breeding along the 
Pacific and Gulf of California coasts, primarily in Mexico (see ``Range 
and Distribution'' section below) (Molina and Erwin 2006, pp. 271-272).
    Bancroft (1929, pp. 283-286) described Gelochelidon nilotica 
vanrossemi from specimens collected at the Salton Sea, Imperial County, 
California. According to Bancroft (1929, p. 284), van Rossem's gull-
billed tern differs from the nominate subspecies of the Old World (G. 
n. nilotica) by its shorter tail and bill shape (less angular gonys), 
and from the subspecies of eastern North America, G. n. aranea, by its 
``decidedly larger size.'' However, in contrast to the petitioner's 
assertion that the validity of the subspecies (i.e., its 
distinctiveness) has not been questioned (CBD 2009, p. 4), information 
in the scientific literature indicates that some authors have 
questioned the distinctiveness of van Rossem's gull-billed tern. For 
example, Murphy (1936, p. 1093) noted the paucity of specimens from the 
New World and concluded ``existing subspecific names have been created 
far in advance of any adequate study of the facts.'' Murphy's published 
statements of dissatisfaction over the available information, in turn, 
caused Grinnell and Miller (1944, p. 172) to ``not recognize a western 
race'' (i.e., subspecies) of gull-billed tern in their authoritative 
review of the birds of California. Although additional specimens are 
now available, providing larger sample sizes in mensural (measurement) 
data, geographic representation of specimens from western North 
America, especially from Mexico and Central America, are still limited 
(Molina and Erwin 2006, pp. 273, 283, and 294-295).
    Individual gull-billed terns are typically not identifiable to 
subspecies under field conditions, and because the two North American 
subspecies are distinguished on the basis of average morphometric 
differences that show substantial overlap, even individual specimens 
are not necessarily distinguishable in the hand (Molina and Erwin 2006, 
p. 283). This suggested to Unitt (2004, p. 249) that the 
distinctiveness of the G. n. vanrossemi as a subspecies remains not 
entirely conclusive (see also Patten and Unitt (2002, pp. 26-35) 
regarding the pitfalls of differentiating subspecies based on average 
differences). Moreover, Pyle (2008, p. 706) stated that the 
morphological differences of the western North American gull-billed 
terns are ``too slight for subspecific recognition.''
    In contrast, other authors have not questioned the distinctiveness 
of Gelochelidon nilotica vanrossemi as a subspecies. For example, the 
American Ornithologists' Union (AOU) Committee on Classification and 
Nomenclature (AOU Committee), the long-standing scientific body 
responsible for standardizing North American avian taxonomy, recognized 
G. n. vanrossemi in its 1957 (fifth) edition of its checklist of North 
American birds (AOU 1957, p. 233), which was the last time the AOU 
Committee explicitly addressed subspecies (AOU 1998, p. xii). More 
recently, Patten et al. (2003, pp. 1-363), who critically reviewed the 
taxonomy of subspecies in their book on the birds of the Salton Sea 
region (Patten et al. 2003, p. 71), also recognized G. n. vanrossemi as 
valid (distinctive) (Patten et al. 2003, p. 188). Additionally, G. n. 
vanrossemi is recognized by many other authors (such as Parnell et al. 
1995, p. 3; Gochfeld and Burger 1996, p. 645; Patten et al. 2001, p. 
45; Dickinson 2003, p. 149; Molina and Erwin 2006, p. 273, but see p. 
283; and Molina et al. 2010, p. 1). However, the authors of this latter 
group of works may not have conducted taxonomic assessments of their 
own and may instead have relied upon other publications. Thus, in 
total, the available scientific literature is not consistent regarding 
the distinctiveness of van Rossem's gull-billed tern.
    The Service is currently funding the U.S. Geological Survey to 
conduct a genetics-based study that may yield additional information 
regarding the distinctiveness between the eastern and western North 
American subspecies of the gull-billed tern, but only those two 
subspecies. As of the preparation of this status review and 12-month 
finding, the results of this work are not yet available. Although we 
anticipate the information from this study will be helpful in 
understanding the relationship between the eastern and western 
subspecies of gull-billed terns in North America, a comprehensive, 
rangewide review is needed to address fully the distinctiveness of all 
of the subspecies, including Gelochelidon nilotica vanrossemi, that 
compose the gull-billed tern species. We are not aware of any modern, 
rangewide treatments that evaluate the taxonomic distinctiveness of 
gull-billed tern subspecies.
    In summary, the available scientific information presents differing 
opinions regarding the distinctiveness of Gelochelidon nilotica 
vanrossemi as a subspecies. Although this contradicts the petitioner's 
assertion that the subspecies' distinctiveness has never been 
questioned (CBD 2009, p. 4), the available information does not 
conclusively support the abandonment of a long-standing, established 
taxon that is accepted by the AOU Committee and is widely used in the 
literature. Therefore, for the purposes of evaluating the petitioned 
action, we assume G. n. vanrossemi, van Rossem's gull-billed tern, is a 
subspecies per section 3(16) of the Act.
Range and Distribution
    Van Rossem's gull-billed terns are migratory (Molina et al. 2010, 
p. 5), which means they breed in one area during the spring and summer 
and then move (migrate) to a different area for the winter. Like most 
birds in the Northern Hemisphere, they nest in northerly locations 
during the summer and overwinter farther south, presumably using the 
Pacific coast of North America as a migratory route (Molina et al. 
2010, p. 5). In the U.S. portion of the subspecies' breeding range, 
where monitoring is more intensive and data sets are more complete, van 
Rossem's gull-billed terns generally arrive in mid-March and leave in 
late August, although some birds stay until September or October 
(Patten et al. 2003, p. 188; Patton 2009, Table 2). Less is known about 
the migratory habits of populations in Mexico.

[[Page 58652]]

    Nesting of what would later be described as the van Rossem's 
subspecies of gull-billed tern was first noted at the Salton Sea in 
1927 (Pemberton 1927, pp. 253-258). Reports of historical observations 
and museum specimen data suggested van Rossem's gull-billed terns bred 
in Mexico (van Rossem and Hachisuka 1937, p. 333; Friedmann et al. 
1950, p. 107; Binford 1989, p. 115; Molina and Erwin 2006, pp. 273-274 
and 294-295), but it was not until the 1990s that nesting of the 
subspecies was actually observed in that country (Palacios and Mellink 
2007, p. 214). The majority of nesting locations were discovered in 
Mexico only after 2000 as a result of focused surveys (Palacios and 
Mellink 2007, p. 217).
    As detailed below, the current breeding range for van Rossem's 
gull-billed tern is western North America from extreme southern 
California in the United States to the State of Guerrero in Mexico. 
Within this general range, the subspecies occurs in discrete nesting 
locations predominantly along the Pacific coast of Mexico including the 
Gulf of California (Molina and Erwin 2006, p. 273) (Table 1, Figure 1). 
An additional coastal nesting colony is located in San Diego Bay, San 
Diego County, California (Molina 2008, p. 188). Nest colonies are also 
located at inland localities in northeastern Baja California, Mexico 
(Molina and Garrett 2001, p. 25; Palacios and Mellink 2007, p. 215), 
and at the Salton Sea, Imperial County, California (Pembarton 1927, p. 
253; Molina 2004, p. 94; Molina 2009b, p. 5). The Salton Sea and San 
Diego Bay are currently the only locations where the subspecies nests 
in the United States (Molina and Erwin 2006, p. 273), and together they 
define the northern extent of the breeding range of van Rossem's gull-
billed tern. However, as this document was being finalized, a pair of 
van Rossem's gull-billed terns attempted to nest at the San Joaquin 
Marsh and Wildlife Sanctuary in Irvine, Orange County, California 
(Daniels 2011, in litt.), which is roughly 135 kilometers (km) (85 
miles (mi)) north of the San Diego Bay nesting location. It is too 
early to know whether this location will be regularly used by the 
subspecies in the future.

 Table 1--List of Known Nesting Locations of Van Rossem's Gull-Billed Tern (Gelochelidon nilotica vanrossemi) in
                             the United States and Mexico (Arranged North to South)
  [Approximate population size over the past decade for coarse-scale comparisons (Large--typically greater than
         100 pairs, Medium--typically between 15 and 100 pairs, and Small--typically less than 15 pairs]
----------------------------------------------------------------------------------------------------------------
                                                               Population size
    Country             State          Nesting location \a\          \b\                  Citations \c\
----------------------------------------------------------------------------------------------------------------
U.S............  California........  Salton Sea (multiple     Large...........  Pembarton 1927, p. 253; Molina
                                      nest sites).                               2004, pp. 92-99; Molina 2010b,
                                                                                 in litt., p. 3.
U.S............  California........  San Diego Bay..........  Medium..........  McCaskie 1987, p. 1488; Patton
                                                                                 2009, Table 2.
Mexico.........  Baja California...  Campo Geot[eacute]rmico  Large...........  Molina and Garrett 2001, p. 24;
                                      Cerro Prieto                               Palacios and Mellink 2007, p.
                                      (including Las                             217; Erickson et al. 2009, p.
                                      Arenitas).                                 508; Molina 2010b, in litt., p.
                                                                                 3; Palacios 2010, p. 11.
Mexico.........  Baja California...  Isla Montague, Colorado  Large...........  Palacios and Mellink 1993, p.
                                      River Delta.                               259; Peresbarbosa and Mellink
                                                                                 1994, p. 201; Peresbarbosa and
                                                                                 Mellink 2001, p. 266; Molina et
                                                                                 al. 2006, p. 5; Palacios and
                                                                                 Mellink 2007, p. 217; Molina
                                                                                 2010b, in litt., p. 3; Palacios
                                                                                 2010, p. 11.
Mexico.........  Baja California     Laguna Ojo de Liebre     Small...........  Danemann and Carmona 2000, pp.
                  Sur.                (Salinas de Guerrero                       195-199; Palacios and Mellink
                                      Negro).                                    2007, p. 217; Palacios 2010, p.
                                                                                 11.
Mexico.........  Sinaloa...........  Bah[iacute]a Santa       Small...........  Gonz[aacute]lez-Bernal et al.
                                      Mar[iacute]a                               2003, p. 176; Mu[ntilde]oz del
                                      (including Isla El                         Viejo et al. 2004, pp. 191-202;
                                      Rancho and Isla                            Palacios and Mellink 2007, p.
                                      Altamura).                                 217; Palacios 2010, p. 11.
Mexico.........  Sinaloa...........  Bah[iacute]a de Ceuta..  Small...........  Gonz[aacute]lez-Medina and
                                                                                 Guevara-Medina 2008, p. 6;
                                                                                 Palacios 2010, p. 11.
Mexico.........  Sinaloa...........  Laguna del Caimanero     Medium..........  Palacios and Mellink 2007, p.
                                      (Las Tres Tumbas).                         217; Palacios 2010, p. 11.
Mexico.........  Sinaloa/Nayarit...  Marismas Nacionales      Large...........  Palacios and Mellink 2007, p.
                                      (including Estero                          217; Palacios 2010, p. 11.
                                      Teacap[aacute]n and
                                      Laguna Pericos (Laguna
                                      las Garzas), Nayarit).
Mexico.........  Colima............  Laguna Cuyutl[aacute]n.  Medium..........  Palacios and Mellink 2007, p.
                                                                                 217; Palacios 2010, p. 11.
Mexico.........  Guerrero..........  Laguna Potos[iacute]...  Small...........  Mellink et al. 2009, p. 8.
----------------------------------------------------------------------------------------------------------------
\a\ Nesting locations are general areas that may comprise more than one nest site. Some locations may not be
  occupied every year.
\b\ The population size is for general comparison only; the level of accuracy and precision varies between
  sources and nesting populations differ from year to year.
\c\ Citations include noteworthy sources for the nesting location as well as sources for population ranges.


[[Page 58653]]

[GRAPHIC] [TIFF OMITTED] TP21SE11.000

    The southern limit to the breeding range of van Rossem's gull-
billed tern is not precisely known. The southernmost location where van 
Rossem's gull-billed terns have been observed nesting is Laguna 
Potos[iacute] in the Mexican State of Guerrero (Table 1, Figure 1). 
Information in the literature shows that gull-billed terns occur during 
the breeding season in small numbers in Mexico south of Laguna 
Potos[iacute] (Binford 1989, p. 115; Mellink et al. 1998, p. 381; 
Molina and Erwin 2006, pp. 294-295; Palacios and Mellink 2007, p. 220). 
Although actual nesting has never been observed at any of these 
southern locations, breeding is suspected at some (for example, Binford 
1989, p. 115; Mellink et al. 1998, p. 381). These areas are all within 
the winter range of the subspecies (Figure 1) and nonbreeding birds may 
remain in this region during the breeding season (Howell and Webb 1995, 
p. 303), which is a confounding factor in assessing observations that 
do not include actual detections of nests.
    Additionally, Table 1 only includes locations where actual nesting 
has been observed, but breeding behavior (such as courtship) has been 
noted at other locations, suggesting nesting may be more widespread. 
These other locations with observed breeding behavior but without 
observation of actual nests include locations in the Mexican States of 
Sonora (historically) (van Rossem and Hachisuka 1937, p. 333) and 
Jalisco (Mellink et al. 2009, p. 48), both of which are within the 
range van Rossem's gull-billed terns are known to nest. Additionally, 
nesting may occur in Mexico near or along the Colorado River, north of 
the known nesting location of Isla Montague at the delta (Erickson et 
al. 2005, p. 498). Moreover, there are likely smaller ephemeral sites 
that are not used every year that are probably missed during 
inconsistent survey efforts. Also, gull-billed terns have been observed 
nesting at inland locations in Mexico (G[oacute]mez de Silva 2005, p. 
501; Molina and Erwin 2006, p. 274), which may consist of colonies 
containing either North American subspecies.
    Although some gull-billed tern specimens from south of Guerrero 
have been identified as van Rossem's gull-billed terns (Hellmayr and 
Conover 1948, p. 297; Binford 1989, p. 115), the majority of the 
occurrences reported in the available literature are field 
observations; thus, these records have not been identified to 
subspecies. Gull-billed terns also nest farther south along the Pacific 
coast of South America; however, specimen data suggest that at least 
some of these birds are the ``eastern'' subspecies of gull-billed tern, 
Gelochelidon nilotica aranea (Molina and Erwin 2006, p. 283; but see 
Hellmayr and Conover 1948, p. 297, footnote 1). The northern extent of 
the range of the Pacific-breeding birds presumed to be G. n. aranea is 
not known and could potentially include Central America, where 
available data are limited. Thus, the southern limit of the breeding 
range of van Rossem's gull-billed tern extends at least as far south as 
Guerrero, and possibly farther south, but survey information from these 
southern areas is limited and any

[[Page 58654]]

conclusions drawn from observational data are confounded by the 
potential occurrence of birds of the ``eastern'' subspecies, G. n. 
aranea.
    The winter range of the subspecies includes the Gulf of California 
and the Pacific coast of mainland Mexico, possibly Pacific coastal 
Central America and coastal northwestern South America (Molina and 
Erwin 2006, p. 272; Molina et al. 2009a, pp. 2-20; Molina et al. 2010, 
p. 1), with the largest concentrations found in the extensive coastal 
lagoon systems of southern Sonora, Sinaloa, and northern Nayarit 
(Molina et al. 2009a, p. 9). However, similar to the breeding range, 
the southern part of the winter range is poorly defined (Molina et al. 
2009a, pp. 9-11). Although at least one specimen collected from 
Guatemala in winter (Molina and Erwin 2006, p. 294) was thought to be 
Gelochelidon nilotica vanrossemi (Hellmayr and Conover 1948, p. 297), 
the potential mingling of the ``eastern'' subspecies of gull-billed 
terns along the Pacific coast of southern Mexico and Central America 
complicates our ability to delineate the winter range of van Rossem's 
gull-billed tern (Molina et al. 2009a, p. 15). Not only are individuals 
of the G. n. aranea subspecies that breed in western South America 
possible in the region (the available literature is not specific as to 
the winter range of these South American-nesting birds), individuals 
that breed in eastern North America (G. n. aranea) may also cross from 
the Gulf of Mexico (such as at the Isthmus of Tehuantepec or Isthmus of 
Panama) to winter along the Pacific coast (Gochfeld and Burger 1996, p. 
645; Molina and Erwin 2006, pp. 283-284).
    Such behavior has been documented for other species of terns and 
gulls (Molina and Erwin 2006, p. 84). As such, ``eastern'' gull-billed 
terns potentially intermingle with van Rossem's gull-billed terns 
within the southern portion of the latter's range. However, we do not 
know how prevalent this is. Moreover, the available literature has 
evolved through time. Contrary to earlier accounts (for example, AOU 
1957, p. 233; Molina and Erwin 2006, p. 282), Molina et al. (2009a, p. 
15) suggested that the winter range may not extend south of the Isthmus 
of Tehuantepec; thus, without firm data the subspecies' range remains 
equivocal. In addition to coastal locations, small numbers of gull-
billed terns, presumably van Rossem's gull-billed terns, regularly 
occur at inland sites in western Mexico during the winter, away from 
Pacific coastal lowlands (Molina et al. 2010, p. 12); thus, the winter 
range likely includes inland areas of western Mexico and possibly 
Central America.
    The best available information indicates the breeding range of the 
subspecies has expanded in recent years. The first record for coastal 
California (and the first record for the Pacific coast north of the 
southern tip of the Baja California Peninsula) was of an adult detected 
along San Diego Bay in July 1985 (McCaskie 1985, p. 962). Evidence of 
nesting was noted there two years later (McCaskie 1987, p. 1488; Unitt 
2004, p. 248). Initially, the population grew slowly and sporadically, 
but after 1999 the population increased much more quickly and steadily, 
totaling approximately 59 pairs in 2010 (R. Patton, in litt., 2010, 
spreadsheet summary). Moreover, despite multiple earlier explorations 
of the avifauna of the Baja California Peninsula, Mexico (Bryant 1889, 
pp. 237-320; Grinnell 1928, p. 61; Wilbur 1987, pp. 94-95; Massey and 
Palacios 1994, pp. 45-57), van Rossem's gull-billed terns were only 
first noted in 1995 as nonbreeders along the Pacific coast of the Baja 
California Peninsula (Erickson et al. 2001, p. 125) and first found 
nesting in 1996 at Laguna Ojo de Liebre near Guerrero Negro, Baja 
California Sur (Danemann and Carmona 2000, p. 197). Laguna Ojo de 
Liebre is the only known coastal nesting location on either coast of 
the 1,200-km-long (750-mi-long) peninsula (Molina et al. 2010, p. 61). 
The colonization of these two new coastal nesting locations suggests 
the breeding range of the subspecies has expanded in recent years.
    Such range expansions are not unprecedented; other colonial 
waterbird species have similarly expanded their range along the Pacific 
coast and established nesting colonies, such as the elegant tern 
(Thalasseus elegans) (Collins et al. 1991, pp. 393-395) and the black 
skimmer (Rynchops niger) (Palacios and Alfaro 1992, pp. 173-176; 
Collins and Garrett 1996, pp. 127-135; Danemann and Carmona 2000, p. 
197). Black skimmers have also moved northward along the Gulf of 
California coast and even inland at the north end of the Gulf; for 
example, establishing nesting colonies at the Salton Sea (McCaskie et 
al. 1974, pp. 337-338; Collins and Garrett 1996, pp. 127-135) and Cerro 
Prieto (Molina and Garrett 2001, p. 25). Van Rossem's gull-billed terns 
use similar nesting habitat as black skimmers, often nesting near one 
another at locations where their ranges overlap (Parnell et al. 1995, 
p. 9). Although the timing of the range expansion of van Rossem's gull-
billed terns has lagged behind the black skimmer and other species with 
expanding ranges, it is possible that van Rossem's gull-billed terns 
may be following a similar pattern and could start to colonize new 
nesting locations along the Pacific Coast.
    There is some indication that van Rossem's gull-billed terns may 
potentially continue to expand their range northward along the 
California coast. Birds that migrate long distances, such as van 
Rossem's gull-billed terns, have the potential to occur outside their 
expected range (i.e., vagrancy). Other subspecies of gull-billed terns 
are capable of long-distance flights and we assume van Rossem's gull-
billed terns are similarly capable. For example, an individual of the 
nominate (European) subspecies was banded as a nestling in Denmark and 
collected a few months later in Barbados in the Lesser Antilles in the 
western Atlantic Ocean (Lincoln 1936, p. 331; see also Cooke 1945, p. 
128)--roughly 4,500 km (3,000 mi) outside of its expected winter range 
in western Africa (Gochfeld and Burger 1996, p. 645). Another gull-
billed tern, probably of the Asian subspecies Gelochelidon nilotica 
affinis (G. c. addenda), was observed on the Hawaiian islands of O'ahu, 
Moloka'i, and Maui over a span of several months (Pyle and Pyle 2009, 
no page number), more than 8,000 km (5,000 mi) away from its expected 
winter range in Southeast Asia (Gochfeld and Burger 1996, p. 645). 
Although we do not have information on similar long-distance, 
extralimital movements for van Rossem's gull-billed tern, birds 
presumed to be of this subspecies have been observed north of the San 
Diego Bay region (the northernmost nesting location within the 
subspecies' expected range), including multiple detections of single 
birds along the California coast as far north as the San Francisco Bay 
area (Patton 2009, Appendix B) and at inland locations along the 
Colorado River and elsewhere in Arizona (Speich and Witzeman 1973, p. 
148; Monson and Phillips 1981, p. 50; Rosenberg et al. 1990, p. 193).
    Such movements of van Rossem's gull-billed terns, though not 
unexpected, occur too infrequently to consider these areas as part of 
the subspecies' range. However, the number of detections of van 
Rossem's gull-billed terns farther north along the coast of California 
has increased as the San Diego Bay breeding population has increased 
(see discussion below in the ``Population Size'' section). As such, 
areas where other species of terns nest along the coast north of San 
Diego should be monitored for nesting gull-billed terns. Confirmation 
of van

[[Page 58655]]

Rossem's gull-billed terns nesting north of San Diego Bay, like the 
recent nesting attempt detected in Orange County mentioned above, would 
indicate a continuing northward expansion of the subspecies' breeding 
range.
    In summary, the current breeding range of van Rossem's gull-billed 
tern extends from San Diego and the Salton Sea along the Pacific and 
Gulf of California coasts to at least as far south as the State of 
Guerrero in Mexico. Actual nesting locations are discontinuously 
distributed within that range (Table 1). However, survey information is 
limited for most of the Pacific coast of Mexico; additional efforts may 
yet detect other nesting locations in this region, including south of 
Guerrero. The current winter range of the subspecies includes the west 
coast of mainland Mexico, potentially as far south as Central America 
and coastal northwestern South America, plus a few inland locations.
Population Size
    Historical data on population sizes are generally lacking for the 
subspecies, especially in western Mexico and farther south into Central 
and South America. As noted above, historical information shows that 
van Rossem's gull-billed terns occurred in Mexico, but these data 
largely consist of anecdotal observations or museum collections 
(specimens); there are few data to indicate the size of historical 
populations of van Rossem's gull-billed terns. Available literature 
that include information on the historical avifauna of western Mexico, 
such as Bryant (1889 pp. 237-320), Brewster (1902, pp. 1-241), Salvin 
and Godman (1904, pp. 1-505), Ridgway (1919 pp. 1-852), Mailliard 
(1923, pp. 443-456), Huey (1927, pp. 239-243), Grinnell (1928, pp. 1-
300), van Rossem and Hachisuka (1937, p. 333), van Rossem (1945, p. 
93), Hellmayr and Conover (1948, p. 297), Friedmann et al. (1950, pp. 
1-204), Schaldach (1963, pp. 1-510), Binford (1989, p. 115), and 
Russell and Monson (1998, pp. 115-116) (see also summary in Palacios 
and Mellink 2007, pp. 214-215), present limited or no information on 
gull-billed terns from the region. Many of the cited historical texts 
predate the 1929 formal description of Gelochelidon nilotica 
vanrossemi, the van Rossem's subspecies of gull-billed tern. Regardless 
of the subspecies or the timing of the historical observations, early 
observers would have been able to identify the species as a whole--G. 
nilotica, the gull-billed tern. As discussed in the Species Description 
and Taxonomy section, the available information indicates that the 
subspecies of the gull-billed tern that breeds in western Mexico (at 
least north of the Isthmus of Tehuantepec) is G. n. vanrossemi. Thus, 
the historical observations of gull-billed terns in western Mexico most 
likely pertained to G. n. vanrossemi. The information that is available 
from these sources indicates that gull-billed terns were rarely 
encountered, and when encountered, were in small numbers. By 
comparison, the information on other species of colonial waterbirds in 
western Mexico is much more complete. Although this list of references 
is not a fully exhaustive list of historical resources, it illustrates 
the contrast between historical information available on gull-billed 
terns and other species of colonial waterbirds that occurred in western 
Mexico. This contrast indicates that the historical scientific 
explorations of the region were adequate to detect many other species 
of colonial waterbirds, but were inadequate to detect gull-billed terns 
or their nest sites in western Mexico. It is reasonable to conclude 
that van Rossem's gull-billed terns were encountered rarely because 
there were comparatively few van Rossem's gull-billed terns to 
encounter. Therefore, we conclude based on the available information, 
the historical population size of van Rossem's gull-billed terns in 
western Mexico was small--or at least not markedly larger than the 
population today.
    In the United States, when Pemberton first discovered the nesting 
colony of gull-billed terns at the Salton Sea in 1927, he estimated 
that there were approximately 500 active nests (Pemberton 1927, p. 
256), which would translate into a similar number of pairs. It is not 
clear when this population became established, but the Salton Sea was 
created in its present form between 1905 and 1907 when Colorado River 
floodwaters filled the dry lakebed known as the Salton Sink; however, 
previous historical and prehistorical floods also periodically filled 
the Salton Sink from time to time (with intervening dry periods), 
forming an intermittent body of water within the Salton Sink now 
referred to as Lake Cahuilla (see Patten et al. 2003, pp. 1-6 for a 
history of Lake Cahuilla and the Salton Sea). Although the Salton Sea 
population of van Rossem's gull-billed terns was not systematically 
monitored until the 1990s, anecdotal evidence shows that the population 
decreased over time to a low somewhere in the range of 15 to 25 pairs 
in the early 1970s (Grinnell and Miller 1944, p. 172; Pyle and Small 
1961, p. 31; McCaskie 1973, p. 919; McCaskie 1974, p. 949; McCaskie 
1976, p. 1004; Garrett and Dunn 1981, p. 189; McCaskie pers. comm. 
2010). Over the next few decades, the population at the Salton Sea 
increased to about 100 to 150 pairs, with more consistent monitoring 
showing that it has remained fairly constant since the early 1990s 
(Molina 2004, p. 94; Molina 2009b, p. 5). In San Diego Bay, the nesting 
population of van Rossem's gull-billed terns has increased from its 
inception in 1987 to 59 pairs in 2010 (R. Patton, in litt., 2010, 
spreadsheet summary).
    Today in Mexico, in addition to the new, small colony at Laguna Ojo 
de Liebre, van Rossem's gull-billed terns have colonized the islands in 
the impoundments associated with the Campo Geot[eacute]rmico Cerro 
Prieto (Cerro Prieto geothermal generation facility) in northeast Baja 
California. The facility started operation in 1973 (Guti[eacute]rrez-
Galindo et al. 1988, p. 201) and van Rossem's gull-billed terns have 
been observed there since at least 1996 (Molina and Garrett 2001, p. 
25). Since 1996, fairly consistent monitoring at this site indicates 
that it has grown to be one of the largest populations (Table 1). 
Additionally, the nesting colony at Isla Montague has been fairly well 
monitored since 1992 (Palacios and Mellink 1993, p. 259; Molina 2010b, 
in litt.). Although nesting at Isla Montague was only just confirmed in 
1992 (Palacios and Mellink 1993, p. 259), nesting on the island was 
suspected decades earlier based on specimens collected there in the 
spring of 1915 (Friedmann et al. 1950, p. 107; Molina and Erwin 2006, 
p. 294; Molina et al. 2010, p. 61).
    As mentioned in the ``Range and Distribution'' section, gull-billed 
terns have been known to occur in western Mexico for more than a 
century (see Molina and Erwin 2006, p. 294) and breeding there was 
likely; however, nesting has only been documented recently. Surveys at 
nesting locations throughout the remainder of the breeding range of van 
Rossem's gull-billed tern in Mexico have been sporadic and essentially 
consist of ``snapshots'' of nesting efforts over time. During the 
breeding seasons of 2003 and 2005, Palacios and Mellink (2003, pp. 1-
66; 2006, pp. 1-84; 2007, pp. 214-222) surveyed at least 367 potential 
nesting areas along the Pacific and Gulf of California coasts of 
Mexico. Additionally, of the nine known nesting locations in Mexico 
(Table 1), all but Laguna Potos[iacute] were resurveyed in June and 
early July 2010 (Palacios 2010, pp. 1-28). However, the level of survey 
effort compared with the number of potential nesting locations along 
the coast of Mexico suggests additional

[[Page 58656]]

undetected nesting locations likely exist. For example, one of the 
largest single colonies of this subspecies (105 to 160 pairs) was only 
discovered in 2003 at Laguna Las Garzas (Laguna Los Pericos) in 
Marismas Nacionales, Nayarit (Table 1) (Palacios and Mellink 2003, p. 
11; Palacios and Mellink 2007, p. 217). New (but small) populations 
were also found nesting in 2006 at Bah[iacute]a de Ceuta, Sinaloa 
(Gonz[aacute]lez-Medina and Guevara-Medina 2008, pp. 6-7) and in 2007 
at Laguna Potos[iacute], Guerrero (Mellink et al. 2009, p. 8) (Table 
1). Thus, although we expect additional nesting locations to be found 
and population estimates to change, we do not expect refinements in 
those values to alter substantially our understanding of the subspecies 
or our analysis.
    As summarized by Molina et al. (2010, p. 10), 737 to 808 pairs of 
van Rossem's gull-billed terns appear to have nested in western North 
America in 2003 and 2005, with approximately 550 of those nesting in 
Mexico. Because these values generally represent pairs of nesting 
adults counted at nesting sites, there are additional nonbreeding 
individuals that are not represented in these totals, underestimating 
the total population size. Additionally, there may be a limited number 
of pairs nesting at undetected locations. Thus, these rough estimates 
represent the minimum population size for van Rossem's gull-billed 
terns in the United States and Mexico.
    Population data for most of the subspecies' range are incomplete 
over time; thus, population trends are difficult to assess. Data from 
the Salton Sea, which are fairly complete, shows a marked decline in 
population compared to the historical high in 1927, but this population 
has remained fairly stable since the 1990s (Molina et al. 2010, p. 10). 
Although preliminary data suggest the numbers of nesting van Rossem's 
gull-billed terns at the Salton Sea during the 2010 nesting season was 
substantially smaller (Molina, in litt., 2010, p. 3), it is not clear 
whether this is a temporary or longer-term change; marked declines have 
been observed there in the past, but they have been temporary (Molina, 
in litt., 2010, p. 3). The available information from the nesting 
locations in Mexico with the most-complete population data (Isla 
Montague and Cerro Prieto) shows that population sizes at these 
locations are variable (Palacios and Mellink 2007, p. 217). The 
populations at these sites also appear to be connected, with 
individuals moving between these nesting locations and the Salton Sea 
nesting location and, to a lesser extent, the San Diego Bay nesting 
location (Molina and Garrett 2001, p. 26; Molina 2004, p. 98; Palacios 
2010, pp. 12 and 15). In combination, the populations of van Rossem's 
gull-billed terns at Isla Montague, Cerro Prieto, and the Salton Sea 
are annually variable but, when taken together, appear to have been 
fairly stable since the 1990s (see Molina et al. 2006, p. 5; Molina and 
Erwin 2006, p. 279; Palacios and Mellink 2007, p. 217; Molina et al. 
2010, p. 10). Data from central and southern Mexico--the bulk of the 
subspecies' range geographically but not, as suggested by the data, in 
numerical terms--are inadequate to define precise trends, but they do 
not show any precipitous declines (see Molina and Erwin 2006, p. 279; 
Palacios and Mellink 2007, p. 217). Moreover, as discussed above, the 
historical size of the van Rossem's gull-billed tern population in the 
rest of Mexico was likely never large.
Biology
    Van Rossem's gull-billed tern is predominantly a coastal nesting 
species, but it also nests at, or near, certain inland saline lakes 
(Parnell et al. 1995, p. 5; Molina and Erwin 2006, p. 284; Molina et 
al. 2010, p. vii). During the nonbreeding season, van Rossem's gull-
billed terns may occur at either saline or freshwater areas (Molina et 
al. 2010, p. 12), but they are often found foraging over tidal mudflats 
within large lagoons and estuaries (Molina et al. 2009a, p. 12). Like 
other terns, gull-billed terns (including van Rossem's gull-billed 
tern) are predators, but they differ from most other tern species in 
how they forage and in the types of prey they consume. Unlike many 
other tern species that eat only fish caught by shallow dives into 
water, gull-billed terns forage on a variety of prey items, which 
varies by area. For example:
    (1) Gull-billed terns capture flying insects during foraging 
flights (Parnell et al. 1995, p. 5);
    (2) They swoop down and snatch up terrestrial prey (such as small 
crabs, lizards, insects, or small chicks of other bird species) and 
aquatic prey (such as small fish) near the water's surface (Parnell et 
al. 1995, p. 5; Molina and Marschalek 2003, p. i); and
    (3) They land to capture small prey items from the water's surface 
(Parnell et al. 1995, p. 5).
    Moreover, gull-billed terns--the species as a whole, including van 
Rossem's gull-billed terns--are opportunistic foragers (Parnell et al. 
1995, p. 5; Gochfeld and Burger 1996, p. 645; Erwin et al. 1998a, p. 
323; Molina 2009a, p. 6). Not only do they eat a wide variety of prey 
items and forage over wide range of areas, they also may 
opportunistically focus on certain prey items when those items are 
abundant or otherwise readily accessible. For instance, gull-billed 
terns in western Africa were observed preferentially foraging on 
fiddler crabs (Uca tangeri), despite being an energy-poor food source, 
because the crabs were abundant and easier to capture than other, more 
energy-rich prey items (Stienen et al. 2008, p. 243). The diet and 
general foraging habits of van Rossem's gull-billed tern is similar to 
that of other subspecies of gull-billed tern (Molina and Marschalek 
2003, p. 9; Molina and Erwin 2006, pp. 286-287; Molina 2009a, pp. 6-8; 
Molina et al. 2009a, p. 12).
    Thus, van Rossem's gull-billed terns are generalist predators whose 
food appears to be determined more by size and availability of prey 
items rather than strictly by the type of prey. The foraging habitat of 
van Rossem's gull-billed terns consists of open mudflats in tidal 
estuaries, river margins, beaches, salt marshes, freshwater marshes, 
aquacultural impoundments (such as shrimp ponds), and a variety of 
upland habitats including open scrub, pasturelands and irrigated 
agricultural fields and associated canals and drains, and the airspace 
over such areas (Molina and Erwin 2006, p. 284; Parnell et al. 1995, 
pp. 4-5). A university-based study is currently underway in San Diego 
Bay to evaluate the foraging patterns and relative use of areas within 
San Diego Bay and the adjacent coastline; the results of this study are 
not yet available.
    Gull-billed terns, including van Rossem's gull-billed terns, nest 
in colonies of 20 to 50 pairs, although numbers may vary (Parnell et 
al. 1995, p. 9). They display low nest-site fidelity; that is, they are 
not closely tied to any one nest site from year to year, even moving to 
new sites and renesting within the same year (e.g., after disturbance 
or predation events) (Parnell et al. 1995, p. 13; Erwin et al. 1998b, 
p. 970). Groups of van Rossem's gull-billed terns have displayed such 
renesting behavior at the Salton Sea (Molina 2009b, pp. 6-7) and at 
Bah[iacute]a Santa Mar[iacute]a (Palacios and Mellink 2007, p. 218) 
(Table 1). Van Rossem's gull-billed terns also readily take advantage 
of new nest sites or sites that are not available every year (for 
example, Molina 2005, p. 4; Molina 2009b, p. 2). Thus, van Rossem's 
gull-billed terns appear to be opportunistic and adaptable nesters.
    The term ``nest colony'' may refer to the group of birds or a 
geographic location. A nesting location (as used in Table 1) may 
contain more than one colony. In general, a colony consists of

[[Page 58657]]

the terns that occupy a nest site during a particular nesting attempt. 
A nest site is the specific location where a group of terns is nesting. 
Individual terns within a colony may move between nest sites between 
nesting attempts within a given breeding season (within-year 
movements). For example, after nest failure at one nest site, members 
of a colony may move within the same breeding season to one (or more) 
nest sites at a different location (or locations) within the general 
nesting location (Molina et al. 2010, p, 17). We also refer to the 
groups of individuals that collectively use nesting locations as 
``populations.'' Even though it appears that van Rossem's gull-billed 
tern populations return to nesting locations (the general area), groups 
of individuals may establish colonies at different nest sites within 
those general areas from year to year (between-year movements). 
Moreover, these populations are not necessarily fixed over time. 
Because van Rossem's gull-billed terns can fly long distances, 
individuals of a population may move between and among other 
populations, more likely occurring between years but potentially even 
within years. For example, between-year movements among nest locations 
(populations) have been observed in the northern portion of the 
subspecies' range where many individual van Rossem's gull-billed terns 
are banded, which allows specific birds to be resighted, and thus 
tracked, over time (Molina and Garrett 2001, p. 26; Patton 2001, p. 8; 
Molina 2004, p. 98; Palacios 2010, pp. 12 and 15).
    Nests of van Rossem's gull-billed terns consist of shallow scrapes 
with simple adornments, such as rocks, shells, or fish bones (Parnell 
et al. 1995, p. 10). Although some individuals may form pairs during 
migration, breeding activity reaches its peak when birds arrive at 
nesting areas (Sears 1981, p. 192; Parnell et al. 1995, p. 8). The 
breeding season generally occurs from mid-March through August, at 
least within the northern portion of its breeding range (Parnell et al. 
1995, pp. 4 and 9). The timing of nest initiation varies from place to 
place and year to year, with some colonies reinitiating nesting after 
predation or disturbance events and moving to other nearby nest sites 
(Molina 2009b, pp. 6-7). Such renesting can occur repeatedly in one 
nesting season or birds may simply abandon nesting at that nesting 
location for a given year (Molina 2009b, pp. 6-7).
    Nesting habitat for van Rossem's gull-billed terns consists of low, 
open areas on natural and artificial beaches, islands, and levees, 
usually with no or sparse vegetation (Parnell et al. 1995, pp. 5 and 
10; Palacios and Mellink 2007, p. 215). Typically, these areas are 
located on islands or other remote areas where the risk of predation is 
low. Barren areas suitable as nest sites are often kept clear by 
natural or artificial disturbance regimes, especially tidal inundation, 
that prevent or limit plant growth. Although gull-billed terns 
typically nest in areas above most high tides (Bent 1921, p. 198; 
Parnell et al. 1995, p 4), it is not uncommon for active nests to be 
destroyed by the highest tides (Erwin et al. 1998b, p. 976; 
Peresbarbosa and Mellink 2001, p. 268; Molina and Erwin 2006, p. 286; 
Patton 2009, p. 9).
    At San Diego Bay and the Salton Sea, van Rossem's gull-billed terns 
typically lay two to three eggs per clutch (Parnell et al. 1995, p. 
12). The egg incubation period is 22 to 23 days, and the young fledge 
after 28 to 35 days (Parnell et al. 1995, p. 11). Similar to other tern 
species (see Dunn 1972, pp. 360-366; Buckley and Buckley 1974, pp. 
1053-1063; Shealer and Burger 1995, pp. 93-99), juvenile gull-billed 
terns remain dependent upon their parents for at least 4 weeks after 
fledging and probably longer, during which time they learn to forage 
and fend for themselves (Parnell et al. 1995, p. 12). Thus, van 
Rossem's gull-billed terns only raise one brood per year (Parnell et 
al. 1995, p. 9); any subsequent renesting attempts typically follow a 
disturbance or predation event that occurs early within the breeding 
season.
    Terns that survive to become adults are generally long-lived 
(Gochfeld and Burger 1996, p. 640) with lifespans of 10 to 20 years or 
even more (such as Thompson et al. 1997, p. 15; Cuthbert and Wires 
1999, p. 19; Shealer 1999, pp. 17-18; Buckley and Buckley 2002, p. 18; 
Hatch 2002, p. 25). Lifespan information on the entire gull-billed tern 
species is limited, with even less known about van Rossem's gull-billed 
tern. Other subspecies of gull-billed terns are known to first breed at 
5 years old, but can establish territories at nest sites without 
breeding at 4 years old (Parnell et al. 1995, p. 12). A few van 
Rossem's gull-billed terns of known age have been observed nesting as 
3-year-olds (Molina et al. 2010, p. 6). Banded gull-billed terns have 
been recovered in Europe almost 16 years post-banding, and 14 years 
post-banding in eastern North America (Parnell et al. 1995, p. 12). 
Patton (2009, p. 9) noted a banded van Rossem's gull billed tern that 
was at least 9 years old at the San Diego Bay colony (and presumably 
breeding), and 10-year-old birds have been observed at the Salton Sea 
(Molina et al. 2010, p. 6). We believe the lifespan of van Rossem's 
gull-billed tern to be similar to other tern species (i.e., 10 to 20 
years, possibly more).
Management Actions
    Through our Division of Migratory Birds Management, the Service is 
the lead Federal agency for managing and conserving migratory birds in 
the United States under the Migratory Bird Treaty Act (MBTA). We 
provide national and international leadership in the conservation and 
management of migratory birds by promoting, among the Service and its 
partners, science-based management of both populations and habitat on 
and off Service lands in support of national and international bird 
plans and initiatives.
    In 2002 and 2008, pursuant to the Fish and Wildlife Conservation 
Act of 1980, as amended (16 U.S.C. 2901 et seq.), the Service included 
the gull-billed tern (the species as a whole) in the list of Birds of 
Conservation Concern (USFWS 2002, pp. 1-99; USFWS 2008, pp. 1-87). The 
species was included as a Bird of Conservation Concern both nationally 
and in certain specific Bird Conservation Regions, including the U.S. 
portions of Bird Conservation Regions 32 (Coastal California) and 33 
(Sonoran and Mojave Deserts) (USFWS 2008, pp. 48 and 49). The gull-
billed tern subspecies that occurs in Bird Conservation Regions 32 and 
33 is the van Rossem's gull-billed tern (Gelochelidon nilotica 
vanrossemi).
    Conservation and management of van Rossem's gull-billed tern is one 
of the Service's regional priorities and includes the following 
activities:
    (1) Fall 2008--We funded a U.S. Geological Survey (USGS) project to 
clarify taxonomic status of gull-billed terns in North America and 
define population structure and status of the species throughout its 
North American range. Results from this work are expected in 2011.
    (2) September 2009--We held a structured decisionmaking workshop, 
bringing together interested parties to address potential conflicts 
between van Rossem's gull-billed terns and species listed under the 
Endangered Species Act. Results of this workshop are still in 
development.
    (3) Spring/summer 2010--We coordinated van Rossem's gull-billed 
tern population monitoring at Sonny Bono Salton Sea and San Diego Bay 
National Wildlife Refuges. This work included population monitoring to 
determine annual productivity, and implementing measures to improve 
habitat and nesting conditions.

[[Page 58658]]

    (4) Spring/summer 2010--The U.S. Navy along with the Service 
supported and is continuing to support university-based research on 
foraging behavior of van Rossem's gull-billed tern within and around 
San Diego Bay, which will provide insight into main foraging sites and 
frequency of visits to foraging sites. Data analysis is currently 
underway and results are not yet available. Additionally, this work 
will continue in 2011 and planning is underway to expand this research 
to include migration and winter ecology using satellite telemetry 
technology.
    (5) Summer 2010--We funded surveys for nine breeding colonies in 
Western Mexico to gain a better understanding of van Rossem's gull-
billed tern population size and estimate 2010 productivity (Palacios 
2010 draft report).
    (6) Summer 2010--We have been and continue to work on population 
models to assess population and meta-population dynamics of the van 
Rossem's gull-billed tern in California colonies. Modeling will also 
evaluate interactions of van Rossem's gull-billed terns with other tern 
and plover populations in San Diego Bay. Further modeling efforts are 
evaluating effects of management actions on gull-billed tern 
populations with a goal of maintaining or increasing van Rossem's gull-
billed tern numbers in California colonies.
    (7) Fall 2010--We initiated coordination with Mexican biologists, 
the Sonoran Joint Venture, and the Cerro Prieto Geothermal Facility to 
develop a management plan for the facility with an emphasis on best 
management practices for colonial nesting seabirds, including van 
Rossem's gull-billed terns. These discussions and actions will also 
look for additional opportunities for conservation management in Mexico 
(e.g., Las Arenitas Sewage Treatment ponds).
    (8) Fall 2010 and 2011--We are participating in several planning 
efforts for habitat restoration projects at the Salton Sea. Two habitat 
restoration projects are in the planning stages (one by California 
Department of Fish and Game (CDFG) and one by Sonny Bono Salton Sea 
National Wildlife Refuge). These planning efforts will emphasize the 
development of suitable nesting habitat for van Rossem's gull-billed 
terns and other colonial nesting birds.
    (9) Fall 2010 and 2011--We are coordinating the development of 
long-term conservation strategies for the management of colonial 
nesting seabirds in San Diego Bay, including efforts to balance 
management of potentially conflicting species like van Rossem's gull-
billed tern, the California least tern (Sternula antillarum browni), 
and the western snowy plover (Charadrius alexandrinus nivosus).

Summary of Information Pertaining to the Five Factors

    Section 4 of the Act and implementing regulations (50 CFR part 424) 
set forth procedures for adding species to, removing species from, or 
reclassifying species on the Federal Lists of Endangered and Threatened 
Wildlife and Plants. Under section 4(a)(1) of the Act, a species may be 
determined to be endangered or threatened based on any of the following 
five factors:
    (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range;
    (B) Overutilization for commercial, recreational, scientific, or 
educational purposes;
    (C) Disease or predation;
    (D) The inadequacy of existing regulatory mechanisms; or
    (E) Other natural or manmade factors affecting its continued 
existence.
    In making this 12-month finding, information pertaining to van 
Rossem's gull-billed tern in relation to the five factors provided in 
section 4(a)(1) of the Act is discussed below. In making our 12-month 
finding on the petitioned action, we considered and evaluated the best 
available scientific and commercial information.
    In considering what factors might constitute threats to a species, 
we must look beyond the exposure of the species to a factor to evaluate 
whether the species may respond to the factor in a way that causes 
actual impacts to the species. If there is exposure to a factor and the 
species responds negatively, the factor may be a threat and we attempt 
to determine how significant a threat it is. The threat is significant 
if it drives, or contributes to, the risk of extinction of the species 
such that the species warrants listing as an endangered or threatened 
species as those terms are defined in the Act.

Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range

    For this factor, we evaluate the present (current) or threatened 
(anticipated) impacts that may affect the habitat or range of van 
Rossem's gull-billed tern. This factor does not address historical or 
past actions that resulted in destruction, modification, or curtailment 
of the species' habitat or range. Past actions that destroyed, 
modified, or curtailed the species' habitat or range are not threats in 
and of themselves. Any persisting ramifications of such past actions 
that may be threats to the species would be addressed under Factor E 
(other natural or manmade threats), below. However, under Factor A, we 
do look to past actions to inform our evaluation of potential future 
threats affecting the species' habitat or range in that the history of 
past actions allows us to predict the likelihood of such actions 
continuing into the foreseeable future.
    As used here, habitat (in its general sense) is an area that 
contains the physical or biological features that are important to the 
species' biological needs, such as breeding, feeding, or sheltering. As 
highly mobile, migratory birds, van Rossem's gull-billed terns are not 
necessarily confined to one particular area that contains those 
physical or biological features; that is, individuals may move between 
or among areas of habitat. Moreover, as a subspecies of bird that 
migrates seasonally, it breeds in certain areas during the Northern 
Hemisphere spring and summer; it then moves to other areas where it 
spends the winter (although, in some areas, there may be overlap). 
Generally, the habitat needs of van Rossem's gull-billed tern can be 
addressed by grouping its habitat into two habitat types, (1) Foraging 
habitat, which it needs all year, whether during the breeding season 
(and within its breeding range) or during the times it is not breeding 
(within its winter range or while migrating); and (2) nesting habitat, 
which it needs for laying eggs and raising young during the breeding 
season.
    Van Rossem's gull-billed tern foraging habitat, as discussed in the 
``Biology'' section, comprises upland and aquatic areas, including open 
mudflats in tidal estuaries, river margins, beaches, salt marshes, 
freshwater marshes, aquacultural impoundments (such as shrimp ponds), 
and a variety of upland habitats including open scrub, pasturelands and 
irrigated agricultural fields and associated canals and drains, and the 
airspace over such areas. Nesting habitat consists of low, open areas 
on natural and artificial beaches, islands, and levees, usually with no 
or sparse vegetation and are typically located on islands or other 
remote areas where the risk of predation is low.
    As highly mobile, migratory birds, van Rossem's gull-billed terns 
can choose among potential nesting locations and specific nest sites 
within those locations. For a nest site to be suitable, it must have 
suitable foraging habitat nearby, among other considerations. Although 
it is not known how gull-billed terns, including

[[Page 58659]]

van Rossem's gull-billed terns, make such assessments of foraging 
habitat (Biber 1989, p. 89), the available information suggests that 
nesting gull-billed terns are typically not food limited (Erwin et al. 
1999, p. 52). In contrast, breeding black skimmers, which often nest 
near gull-billed terns but eat fish almost exclusively (Gochfeld and 
Burger 1994, pp. 4, 12-13), may often be food limited (Erwin 1977, p. 
715). This suggests that the opportunistic foraging by van Rossem's 
gull-billed tern over a wide range of foraging habitats allows the 
subspecies to have a low sensitivity to impacts to foraging habitat, 
even when confined to smaller geographical areas during the breeding 
season. This, in turn, suggests that the subspecies will have a low 
sensitivity to impacts to foraging habitat during migration and on the 
wintering grounds, when van Rossem's gull-billed terns are even less 
geographically restricted. Moreover, this low sensitivity to impacts to 
foraging habitat, as a natural trait of the subspecies, is unlikely to 
change over the foreseeable future. Because foraging habitat for the 
subspecies includes a wide range of areas and nesting habitat comprises 
specific nest sites, nesting habitat for van Rossem's gull-billed tern 
is likely to be more limited than foraging habitat under most 
situations.
United States
    Salton Sea--The Salton Sea is a large, inland lake in the Imperial 
and Coachella Valleys and is within the Sonoran Desert. The Salton Sea, 
in its present form, was created in the early 1900s by flooding on the 
Colorado River that followed canals dug for irrigation (see Patten et 
al. 2003, pp. 1-6 for a more detailed summary). The Salton Sea has been 
maintained since then by waste irrigation water associated with 
extensive agricultural development in the region. Thus, most of the 
development of the region occurred in the past. Today, the existing 
agricultural fields and associated canals serve as foraging habitat for 
van Rossem's gull-billed terns.
    However, the amount of water being used for agriculture has 
declined because of an agreement to transfer water out of the Imperial 
Valley and some fields in agricultural production are being 
intentionally fallowed to reduce the amount of water used in the 
Imperial Valley (IID 2006, p. 1; IID 2009, p. 71). Which fields are 
fallowed is determined randomly (IID 2006, p. 1), so we expect fallowed 
fields to occur over a wide area in the Imperial Valley and not 
concentrated near areas of van Rossem's gull-billed tern foraging 
activity. Moreover, the practice of fallowing as a water conservation 
measure is temporary; fallowing will end after 2018 (IID 2009, p. 72). 
Over the time fallowing is to be phased out other water conservation 
measures will likely be enacted in the Imperial Valley, some of which 
may affect some areas of foraging habitat for van Rossem's gull-billed 
terns. For example, to conserve water, there may be increased use of 
sprinklers or other irrigation techniques rather than the predominant 
current practice of flooding fields (which makes crickets, an important 
food source (Molina 2009a, p. 1), and other terrestrial prey items more 
accessible as they flee the rising water), even where van Rossem's 
gull-billed terns forage (IID 2007, pp. 17-19; Schoneman 2010, in litt. 
p. 2). However, as noted previously, van Rossem's gull-billed terns are 
opportunistic foragers--they concentrate their foraging activity on 
easily available food sources (Stienen et al. 2008, p. 243)--yet they 
forage on a wide variety of prey items (Parnell et al. 1995, p. 5). As 
such, van Rossem's gull-billed tern foraging habitat includes a number 
of areas. Thus, even if some of the available foraging habitat is 
destroyed or modified, it will likely not affect a substantial amount 
of van Rossem's gull-billed tern foraging habitat because the 
subspecies uses a wide range of areas as foraging habitat and they are 
capable of flying to those areas.
    Van Rossem's gull-billed terns nest at several different sites 
(primarily islands) in the Salton Sea or nearby water bodies. The 
subspecies' use of particular nest sites varies between and within 
years, depending on local conditions. Nest site conditions within the 
Salton Sea vary because the Salton Sea has no outflow and the elevation 
of the lake's surface depends upon the amount of water input and loss. 
Input of water into the Salton Sea is primarily from agricultural 
runoff from nearby Imperial Valley and, to a lesser extent, Coachella 
Valley, with some input also from natural precipitation, which is 
variable and typically scant. Water loss is through evaporation, which 
is high in the desert environment.
    Through recent history, shoreline elevations of the Salton Sea have 
fluctuated. As water levels rose, which was the case through much of 
the mid-twentieth century (Cohen et al. 1999, p. 10), many existing 
islands became submerged and were no longer available for nesting, 
while other small, higher points of land (such as former levees) became 
new islands. Some of the new islands then became nest sites for birds, 
including van Rossem's gull-billed terns (Molina 2004, p. 96). As water 
levels dropped, which has been the case over the past several years, 
many of the small islands (islets), such as those at Johnson Street, 
Elmore Desert Ranch, and Obsidian Butte, have again become part of the 
mainland and have become vulnerable to terrestrial predators, such as 
coyotes (Canis latrans), feral dogs (C. familiaris), or raccoons 
(Procyon lotor) (Molina 2003, p. 2; Molina 2004, p. 96; Molina 2005, p. 
5; Molina 2009b, p. 7; Molina 2010b, in litt., p. 3). The larger Mullet 
Island has remained an island over this time; however, conditions for 
nesting of van Rossem's gull-billed terns at this site have varied 
because of other factors (for example, predation, competition, or 
disturbance) (Molina 2004, p. 96).
    We expect water levels of the Salton Sea to continue to drop in the 
foreseeable future because the amount of water used for irrigation in 
the Imperial Valley (California) has declined and has been transferred 
(sold) to urban areas outside the region, thus limiting the amount of 
agricultural runoff entering the Salton Sea (IID 2006, p. 1). As such, 
even the large Mullet Island is expected to become attached to the 
mainland in the near future (Molina 2010a, p. 9). As the water level 
drops in the foreseeable future, it is likely that most of the 
historical areas of topographical relief that were once islands will 
not again reemerge because most of those areas eroded while inundated 
(see Molina 2001, p. 97). However, the dropping water level of the 
Salton Sea may allow for new islands to become exposed, allowing for 
novel nest sites for van Rossem's gull-billed terns, such as one south 
of Obsidian Butte used by van Rossem's gull-billed terns in 2010 
(Molina 2010a, p. 6).
    In addition to those nesting islands that are or were isolated 
because of the waters of the Salton Sea, van Rossem's gull-billed terns 
opportunistically use nesting habitat on intentionally or accidentally 
created islands in artificial impoundments along the edge or near the 
Salton Sea (Molina 2004, p. 93). For example, the creation of the 
``saline habitat ponds'' near Hazard Road at the southeastern corner of 
the Salton Sea in 2006 (Miles et al. 2009, p. 1), provided nesting 
habitat for the subspecies from 2008 to 2010 (Molina 2009b, p. 2; 
Molina 2010a, p. 8); the ponds were dewatered and decommissioned 
following the 2010 bird nesting season (M. Walker, Bureau of 
Reclamation, pers. comm. 2010). Another example of opportunistic use of 
nesting habitat is the 2005 nesting of van Rossem's gull-billed terns 
at a pond some 25 km (15

[[Page 58660]]

mi) from the Salton Sea that typically is only full during the winter 
but had water during the breeding season that year (Molina 2005, p. 4). 
Although the water levels in such artificial impoundments may be 
independent of the water levels of the Salton Sea, they are also 
variable between and within years. These ponds are dependent upon 
artificial water inputs, and the management of the water levels in some 
of these ponds may not necessarily take into account the needs of 
waterbirds that may be nesting, including van Rossem's gull-billed 
terns. Thus, the literature shows that such ponds have provided, albeit 
inconsistently, nesting habitat for the subspecies.
    Additionally, a few nest sites located on or near the Salton Sea 
are managed for nesting waterbirds, including van Rossem's gull-billed 
tern, especially those on the Sonny Bono Salton Sea National Wildlife 
Refuge (Salton Sea Refuge) (Schoneman 2010, in litt., p. 1). Even so, 
the status of the nest sites on the Salton Sea Refuge is not assured 
over the long term because the Refuge must purchase the water to 
maintain the ponds that allow for the existence of the nesting islands 
and adequate funding is not guaranteed (C. Schoneman, Sonny Bono Salton 
Sea National Wildlife Refuge, pers. comm. 2010). Moreover, the 
availability of the water itself is not guaranteed; for example, during 
a water shortage emergency, water availability may be limited. 
Nevertheless, the Salton Sea Refuge has consistently managed its 
wetlands to support nesting van Rossem's gull-billed terns since 1995 
(Molina 2004, p. 97; Schoneman 2010, in litt., p. 1). Additionally, 
artificial nesting platforms have been used at the Salton Sea Refuge to 
provide additional nest sites for van Rossem's gull-billed terns and 
other waterbird species (Molina 2006, p. 3; Molina et al. 2009b, p. 
267). This or other management actions could potentially be used to 
provide additional nest site options for van Rossem's gull-billed terns 
at the Salton Sea, even without the availability of water for 
artificial ponds.
    In summary, at the Salton Sea, even if some of the available 
foraging habitat is destroyed or modified, it will likely not affect a 
substantial amount of van Rossem's gull-billed tern foraging habitat 
because the subspecies uses a wide range of areas as foraging habitat 
and the birds are capable of flying to those areas. We anticipate some 
loss of existing nesting habitat at the Salton Sea because the Sea's 
decreasing water level will reduce the number of nesting islands that 
the subspecies has traditionally used over the past 10 to 20 years. 
However, the lowering water level may result in the exposure of new 
islands that may serve as nesting habitat, as was shown in 2010. 
Additionally, van Rossem's gull-billed terns have opportunistically 
used suitable nesting habitat in artificial impounds near the Salton 
Sea, even though such habitat may only occur from time to time. Thus, 
we expect some reduction in the amount of nesting habitat (i.e., a 
reduction in the number of nest site options), but we do not expect 
complete elimination of nesting habitat in the region. The anticipated 
reduction in the amount of nesting habitat may force van Rossem's gull-
billed terns to nest in areas where predation, disturbance, or other 
threats may be more likely, potentially resulting in lowered 
productivity of the subspecies at this nesting location. These 
potential threats are addressed in the other factors, below.
    San Diego Bay--The region around San Diego Bay is highly urbanized, 
nearly built-out, as a result of past development, most of which 
occurred before the subspecies colonized the region in 1987. Much of 
south San Diego Bay itself was developed for salt production. Such 
areas of salt production, or ``saltworks,'' comprise a network of dikes 
that creates a series of ponds from which water evaporates, which 
leaves an ever-concentrating solution of sea salt that is eventually 
dried and harvested. The San Diego Bay saltworks area is now part of 
the greater San Diego Bay National Wildlife Refuge. Many of the areas 
of foraging habitat for the subspecies, such as the areas around San 
Diego Bay (including San Diego Bay National Wildlife Refuge, Silver 
Strand State Beach, and certain lands owned or operated by the U.S. 
Navy) and the Tijuana River estuary (including Tijuana Slough National 
Wildlife Refuge and Borderfield State Park) (Patton 2009, pp. 10-11 and 
Figure 2), are largely protected from future development. As such, 
substantial destruction or modification of foraging habitat in the San 
Diego Bay region is not occurring currently nor is it likely to occur 
in the foreseeable future.
    Potential nesting habitat for van Rossem's gull-billed terns occurs 
in undeveloped areas in and around San Diego Bay; nearly all occupied 
nest sites are located on the saltworks dikes on San Diego Bay National 
Wildlife Refuge lands (Patton 2009, p. 8). These nesting sites are 
protected and managed to benefit several species of colonial 
waterbirds, including van Rossem's gull-billed terns (USFWS 2006, pp. 
1-36). Thus, destruction or modification of nesting habitat by urban 
development is not a significant threat to the San Diego Bay colony of 
van Rossem's gull-billed terns.
Mexico
    The availability of information on specific nesting locations in 
Mexico (Table 1; Figure 1) is variable and generally less detailed than 
what is available for nesting locations in the United States. Using the 
information available, the following discussion provides our assessment 
of the status of van Rossem's gull-billed tern foraging and nesting 
habitat at the locations in Mexico. We are not aware of any van 
Rossem's gull-billed tern nesting locations south of Mexico in Central 
America.
    Campo Geot[eacute]rmico Cerro Prieto--The setting at this location 
is very similar to the Salton Sea and has a comparable history of 
agricultural development (Furnish and Ladman 1975, pp. 84-88; Molina 
and Garrett 2001, p. 23). Given the similarity to the Salton Sea, 
foraging by van Rossem's gull-billed terns likely occurs in the 
agricultural fields, along the canals and drains in the area, and over 
the neighboring desert (Molina and Garrett 2001, pp. 23, 25, and 27; 
Erickson et al. 2009, p. 508). The area is not subject to the same 
water agreements as the Imperial Valley. The available literature does 
not identify any significant threats to van Rossem's gull-billed tern 
foraging habitat in the region now or in the foreseeable future.
    Van Rossem's gull-billed terns nest on islands in artificial ponds 
created by the dumping of wastewater (brine) from the geothermal 
electrical generation facility. Since 1996, Cerro Prieto has grown to 
be one of the larger populations of van Rossem's gull-billed terns 
(Molina and Garrett 2001, p. 25; Palacios and Mellink 2007, pp. 215-
216). Recent information suggests the facility is managing its brine 
differently, reducing the amount of water in the ponds, thereby 
reducing the available nesting habitat for van Rossem's gull-billed 
terns (Molina 2010b, in litt., p. 4; Palacios 2010, pp. 11-14). 
However, we do not know if this situation is permanent and, as of 2010, 
the nesting location still had areas of nesting habitat (Palacios 2010, 
pp. 11-14). Additionally, about 100 van Rossem's gull-billed terns were 
seen at the ``new Las Arenitas sewage ponds, near Cerro Prieto'' 
(Erickson et al. 2009, p. 508), but these were likely birds from Cerro 
Prieto and there was no evidence of nesting observed at this site (R. 
Erickson, Regional Editor, North American Birds, 2010, pers. comm.).
    The conditions at Cerro Prieto illustrate the difficulty in 
accurately assessing long-term threats to van

[[Page 58661]]

Rossem's gull-billed tern related to management of artificial water 
impoundments because these areas are managed for reasons other than 
maintaining nesting habitat. Because of the combination of the loss of 
suitable nesting habitat at Cerro Prieto proper, and the uncertainty 
over the subspecies' use of the new Las Arenitas ponds, we are unable 
to predict the future of this population at this nesting location; 
however, because van Rossem's gull-billed terns can opportunistically 
use nesting habitat even under changing conditions (see above), it is 
unlikely that all nesting at this nesting location will cease in the 
foreseeable future.
    Isla Montague--Isla Montague, a large, low island in the Colorado 
River delta at the north end of the Gulf of California in Baja 
California, is part of the breeding range of the subspecies, although 
some birds may winter there, too (Molina et al. 2009a, p. 9). This area 
is within the protective core zone of the Alto Golfo de California y 
Delta del R[iacute]o Colorado Biosphere Reserve (Peresbarbosa and 
Mellink 2001, p. 265). Foraging habitat includes the deltaic and 
coastal areas around the island, including nearby aquacultural shrimp 
ponds (Palacios and Mellink 2006, p. 60). Conversion of areas to shrimp 
aquaculture may destroy or modify areas of natural foraging habitat, 
but it also is likely to result in manmade foraging habitat that can 
have concentrated prey, especially during periods of shrimp harvest 
(Molina et al. 2009a, p. 12). As such, the development of shrimp 
aquaculture is likely not a substantial impact to van Rossem's gull-
billed tern foraging habitat here or elsewhere in the subspecies' 
overall range.
    Since 1992, when nesting was first confirmed at Isla Montague, 
incomplete though somewhat consistent data show that the nesting 
habitat on this island has supported as few as 30 and up to as many as 
200 breeding pairs of nesting van Rossem's gull-billed terns (Palacios 
and Mellink 2007, p. 217; Molina et al. 2010, p. 61). This population 
was larger in 2010, potentially because birds from Cerro Prieto, the 
Salton Sea, or both, relocated to this nesting location (Palacios 2010, 
pp. 14-15). Moreover, the nesting habitat at this site is low in 
elevation and subject to flooding during extreme high tides 
(Peresbarbosa and Mellink 2001, pp. 267-268). Although such flooding is 
a potential threat to eggs or young (see Factor E), it does suggest 
that substantial manmade developments here are unlikely. Therefore, we 
do not anticipate destruction or modification of nesting habitat to be 
a significant threat at this location.
    Laguna Ojo de Liebre--This site is a large lagoon along the Pacific 
coast of the Baja California Peninsula in the northwest corner of Baja 
California Sur. The area is within the El Vizca[iacute]no Biosphere 
Reserve (Palacios 2010, p. 6). Associated with this lagoon is the 
salinas de Guerrero Negro (Guerrero Negro saltworks), an extensive 
system of artificial ponds used in the salt-making process. Foraging 
habitat in the region is likely within the greater lagoon area, 
including portions of the saltworks, and the nearby coastal areas and 
uplands. Small islands within the network of ponds provide potential 
nesting habitat for colonial waterbirds, including a small number of 
van Rossem's gull-billed terns (Danemann and Carmona 2000, p. 197; 
Palacios and Mellink 2006, p. 49; Palacios 2010, p. 16). Although this 
nesting location is noteworthy because it is the only one on the Baja 
California Peninsula, the small number (4 to 14 breeding pairs) of van 
Rossem's gull-billed terns that nest here do not represent a 
significant number of birds relative to the overall population of the 
subspecies. The available information does not suggest that this area 
is used by van Rossem's gull-billed terns during the winter.
    Foraging habitat in the region is likely within the greater lagoon 
area, including portions of the saltworks, and the nearby coastal areas 
and uplands. Although some future development is possible, especially 
near the community of Guerrero Negro, we do not anticipate substantial 
destruction or modification of van Rossem's gull-billed tern foraging 
habitat in this area because much of the area away from Guerrero Negro 
and the saltworks is largely uninhabited and the area is designated a 
biosphere reserve, which may limit any potential future development. 
Even if some development occurs, it will likely not affect a 
substantial amount of van Rossem's gull-billed tern foraging habitat 
because the subspecies uses a wide range of areas as foraging habitat.
    As suggested by the ponds at Cerro Prieto, we should not consider 
the islands associated with the saltworks permanent; however, the 
available information suggests that significant changes in management 
are unlikely over the foreseeable future (Palacios and Mellink 2006, p. 
54; Palacios 2010, p. 16).
    Bah[iacute]a Santa Mar[iacute]a--This area is a large and extensive 
coastal lagoon system with long barrier beaches in Sinaloa. Foraging 
habitat in this area likely includes the greater lagoon, including 
areas of shrimp aquaculture; the coastline; and nearby agricultural 
areas. The nesting habitat for van Rossem's gull-billed terns at 
Bah[iacute]a Santa Mar[iacute]a comprises two low, sandy islands (and 
associated small islets), Isla El Rancho and Isla Altamura, which are 
part of the lagoon's barrier islands (Palacios and Mellink 2007, p. 
218; Palacios 2010, p. 19). Shrimp aquaculture occurs within the large 
bay, and agriculture occurs in nearby uplands (Engilis et al. 1998, p. 
333; DeWalt 2000, pp. 61-62), but the operations appear to be located 
in areas at some distance from the nesting islands (Robadue and 
Villalba 2001, p. 2). The Bahia Santa Maria nesting area is included in 
the Islas del Golfo de California (Gulf of California Island) Park 
System and the Santa Maria Bay Ecosystem Management Program (Molina et 
al. 2010, p. 17; Palacios 2010, p. 7). Areas within this lagoon are 
being conserved for shorebirds and other wildlife species through 
efforts of nongovernmental organizations (Robadue and Villalba 2001, p. 
2; ABC 2007, p. 1). Together, these protections restrict the 
destruction of nesting and foraging habitat for van Rossem's gull-
billed terns in the lagoon. Loss or modification of van Rossem's gull-
billed tern nesting or foraging habitat at Bahia Santa Maria does not 
appear to be a significant threat now or in the foreseeable future.
    Bah[iacute]a de Ceuta--This site is a large, long, coastal lagoon 
with barrier beaches in Sinaloa. Foraging habitat in this area likely 
includes the greater lagoon, including areas of shrimp aquaculture; the 
coastline; and nearby agricultural areas. The area of van Rossem's 
gull-billed tern nesting habitat appears to be at the south end of the 
lagoon near an area of artificial impoundments (Gonz[aacute]lez-Medina 
and Guevara-Medina 2008, p. 7). Mu[ntilde]oz del Viejo et al. (2004, p. 
197), describing perhaps the same location from a study of other 
species of nesting terns, identifies the area as ``a long-abandoned 
saltflat'' (salt production area or saltworks). The nesting habitat at 
this site is low in elevation and subject to flooding during extreme 
high tides, which makes substantial manmade developments here unlikely. 
Gonz[aacute]lez-Medina and Guevara-Medina (2008, p. 7) have stated that 
there seem to be no direct anthropogenic threats to the nesting habitat 
at this site. However, the population of van Rossem's gull-billed terns 
at this nesting location is very small, consisting of less than 10 
individuals and only 1 nest was observed in 2006 (Gonz[aacute]lez-
Medina and Guevara-Medina 2008, p. 6); the nesting

[[Page 58662]]

site, although apparently still present, was not occupied in 2010 
(Palacios 2010, pp. 20-21). Therefore, the available information 
suggests that the nesting and foraging habitat for van Rossem's gull-
billed tern at this location is currently not likely to be destroyed or 
modified now or in the foreseeable future; however, this nesting 
location appears to be only intermittently occupied by a very small 
population of van Rossem's gull-billed terns.
    Laguna del Caimanero--This site is a moderate-size lagoon in 
Sinaloa. Foraging habitat in this area likely includes the greater 
lagoon, including areas of shrimp aquaculture; the coastline; and 
nearby agricultural areas. In 2005, the nesting area for van Rossem's 
gull-billed terns was located on the southeastern part of the lagoon on 
a large, dry, mudflat-island surrounded by tidal channels (Palacios and 
Mellink 2006, p. 66). In 2010, the terns used a different mudflat-
island, as well as a dredge-spoil island (Palacios 2010, pp. 21-22) for 
nesting, which indicates that multiple areas of nesting habitat are 
available in the vicinity. Past agricultural development of the 
surrounding areas has altered the landscape, vegetation, and surface 
flows of water around the lagoon, leading to increased siltation within 
the lagoon (Ruiz-Luna and Berlanga-Robles 1999, p. 37). Additionally, 
shrimp aquaculture is practiced within the lagoon (Galindo et al. 1997, 
p. 1072), including near the nest sites (Palacios and Mellink 2006, p. 
66).
    The lagoon is artificially channelized, which has increased 
siltation in the southeast portion of the lagoon (Hern[aacute]ndez-
Cornejo and Ruiz-Luna 2000, p. 604), which in turn may have contributed 
to the formation of the mudflat-island nest sites. Such islands likely 
flood during high tides in winter (Palacios and Mellink 2006, p. 66), 
which may increase habitat quality because vegetation growth is 
inhibited. However, high tides may also inundate the nest sites during 
the breeding season (Palacios 2010, p. 22), washing away eggs or young 
chicks. Additionally, fishermen used the 2005 mudflat-island nest site 
to beach small boats, and they erected a small, palapa-like shade 
structure in the vicinity (Palacios and Mellink 2006, p. 66). Given the 
limited information we have regarding the current and future human 
activities within this nesting location and variability of use by the 
van Rossem's gull-billed tern, we determine that the destruction or 
modification of nesting or foraging habitat is not a significant threat 
at this location now or in the foreseeable future.
    Marismas Nacionales--A portion of this large, extensive lagoon 
system in northwestern Nayarit, called Marismas Nacionales Nayarit, has 
recently been designated a Natural Protected Area, in the Biosphere 
Reserve category, while the Sinaloa portion of the lagoon has been 
proposed for protection (E. Palacios, pers. comm. 2010). Foraging 
habitat in this area likely includes the greater lagoon (including 
areas of shrimp aquaculture, the coastline, and nearby agricultural 
areas), and we determine that the destruction or modification of 
foraging habitat is not a significant threat at this location now or in 
the foreseeable future. Nesting habitat for van Rossem's gull-billed 
terns at this large site includes Estero Teacap[aacute]n, which 
consists of a barrier beach at the mouth of the lagoon, and some low, 
small islands in Laguna Pericos. Because the nesting habitat at Estero 
Teacap[aacute]n is at the mouth of the lagoon on the barrier beach 
where natural forces are likely to cause changes in the landscape on a 
regular basis, it is unlikely to be lost due to large-scale 
development. However, the nesting area is subject to lesser impacts 
resulting from smaller human activities that might affect the nesting 
habitat of van Rossem's gull-billed terns. The nesting colony in 2003 
appeared to be in use despite the presence of a palapa-style shade 
structure used by fishermen (Palacios and Mellink 2006, p. 71).
    The Laguna Pericos nesting area is within a portion of the lagoon 
that has been altered to promote shrimp harvest, including the creation 
of ponds for shrimp aquaculture (Hern[aacute]ndez-Cornejo and Ruiz-Luna 
2000, p. 604). Further alteration of the area is possible for 
development of shrimp fisheries and aquaculture. Although such 
potential alterations may affect van Rossem's gull-billed tern nesting 
habitat, individual van Rossem's gull-billed terns readily move between 
and among specific nest sites, including manmade areas that provide 
habitat. Because the Marismas Nacionales area is very large with 
multiple small islands, sand bars, and manmade levees and thus suitable 
alternative nest sites, we expect this nesting population has the 
option to move to other available sites to nest, if necessary. 
Therefore, we determine that destruction or modification of nesting 
habitat is not a significant threat to the van Rossem's gull-billed 
tern at this location now or in the foreseeable future.
    Laguna Cuyutl[aacute]n--Compared to the extensive lagoons in 
Sinaloa and Nayarit, Laguna Cuyutl[aacute]n in the Mexican State of 
Colima is relatively small, but it is the largest lagoon in a roughly 
1,150-km (700-mi) stretch of coastline (Mellink and Riojas-L[oacute]pez 
2009, p. 1). Foraging habitat in this area likely includes the greater 
lagoon (including areas of shrimp aquaculture, the coastline, and 
nearby agricultural areas), and we determine that the destruction or 
modification of foraging habitat is not a significant threat at this 
location now or in the foreseeable future. Nesting habitat for van 
Rossem's gull-billed terns consists of a number of small natural and 
artificial islands in the lagoon (Palacios and Mellink 2006, pp. 77-
84). The lagoon is divided into several subareas. The northwesternmost 
portion of the lagoon is dredged regularly to provide shipping access 
for the industrial port city of Manzanillo and is subject to oil spills 
and additional development (Mellink and Riojas-L[oacute]pez 2009, pp. 
5-7). One island used by nesting van Rossem's gull-billed terns in 2005 
is located in this portion of the lagoon (Palacios and Mellink 2006, p. 
83). This island was created as a byproduct of past dredging (Palacios 
and Mellink 2006, p. 83). The other islands used for nesting by van 
Rossem's gull-billed terns in 2005 are located in a shallower portion 
of the lagoon to the southeast. The nest site near Manzanillo is likely 
to be destroyed by future dredging or other port-improvement or 
development projects. The other nesting area used by van Rossem's gull-
billed terns is in a portion of the lagoon at some distance from 
Manzanillo, and we determine that development is not likely to 
significantly threaten nesting habitat for van Rossem's gull-billed 
terns in this portion of the lagoon in the foreseeable future.
    Laguna Potos[iacute]--This site is a relatively small lagoon system 
in Guerrero. Foraging habitat in this area likely includes the greater 
lagoon (including areas of shrimp aquaculture, the coastline, and 
nearby agricultural areas), and we determine that the destruction or 
modification of foraging habitat is not a significant threat at this 
location now or in the foreseeable future. The nesting habitat for van 
Rossem's gull-billed terns at this location consists of low areas of 
salt flats (Mellink et al. 2009, p. 44). The nest site is subject to 
flooding during high rains (which typically occur during the latter 
part of the nesting season), but the best available information 
suggests the nest site is located away from human activities and is, 
therefore, protected from loss or modification (Mellink et al. 2009, p. 
51); thus, this area does not appear to be significantly

[[Page 58663]]

threatened with development now or in the foreseeable future.
Other Areas of West Mexico and Central America
    We are not aware of any current (confirmed) nesting locations south 
of Laguna Potos[iacute], Mexico. Although areas of far-southern Mexico 
and Central America may potentially be within the breeding range of the 
species, Molina et al. (2009a, p. 15) suggest that it is unlikely that 
``appreciable'' breeding populations occur south of the Isthmus of 
Tehuantepec. Therefore, even if habitat destruction and modification is 
occurring in this region, it is not a significant threat to van 
Rossem's gull-billed tern now or in the foreseeable future.
    During the nonbreeding season, when the subspecies is migrating or 
is within its winter range, van Rossem's gull-billed terns may use 
other sites along the Pacific coasts of Mexico and (possibly) Central 
America. Foraging habitat may include a wide array of areas. As noted 
in the ``Biology'' section, above, van Rossem's gull-billed terns are 
opportunistic, often focusing on easy-to-catch prey items. For example, 
in western Mexico, wintering van Rossem's gull-billed terns were 
observed foraging at aquacultural shrimp ponds where prey is 
concentrated (Molina et al. 2009a, p. 12). Tidal flats and seasonally 
flooded flats were also found to be widely used as foraging areas 
during the winter (Molina et al. 2009a, p. 8). Although coastal 
development is occurring (Molina et al. 2009a, p. 14), there are other 
areas that have been designated or are proposed to become designated as 
Natural Protected Areas, including biosphere reserves, where 
development is less likely (see Factor D). Additionally, as noted 
above, the development of shrimp aquaculture does not necessarily 
result in the elimination of foraging habitat. Moreover, the subspecies 
is not tied to any one particular geographical area or even to any one 
type of foraging area within its winter range. Thus, destruction or 
modification of van Rossem's gull-billed tern foraging habitat in 
western Mexico is not likely a significant threat now, nor is it likely 
to be within the foreseeable future.
    It is unclear whether or to what extent van Rossem's gull-billed 
terns actually winter in Central America. Even if they do occur there, 
Molina et al. (2009a, p. 15) suggest that it is unlikely that 
``appreciable'' wintering populations occur south of the Isthmus of 
Tehuantepec, Mexico. Moreover, the subspecies is not tied to any one 
particular geographical area or even to any one type of foraging area 
within its winter range. Thus, it is unlikely that the subspecies would 
be significantly affected by any destruction or modification of its 
foraging habitat in Central America now or within the foreseeable 
future.
Summary of Factor A
    Van Rossem's gull-billed tern foraging habitat includes a wide 
range of areas, including wetlands and uplands, and van Rossem's gull-
billed terns forage opportunistically within these areas. Moreover, van 
Rossem's gull-billed terns are highly mobile, capable of locating and 
utilizing different foraging areas. Loss or modification of foraging 
habitat does not appear to be a significant threat to van Rossem's 
gull-billed tern for the south San Diego Bay population, and a wide 
range of foraging habitat at Salton Sea will be maintained such that 
losses or modification of some foraging habitat areas do not constitute 
a significant threat to the Salton Sea population. The assessment of 
loss or modification of foraging habitat in Mexico and Central America 
is more difficult to determine because the quantity and specificity of 
the available information is variable across the region. It is even 
questionable whether the subspecies occurs south of the Isthmus of 
Tehuantepec in southern Mexico. However, because of the subspecies' 
ability to forage in a wide range of areas, including areas developed 
for aquacultural shrimp ponds, the subspecies is less susceptible to 
destruction and modification of its foraging habitat. Additionally, it 
is not likely that the foraging areas in Mexico and Central America 
will be substantially affected by development, in part because many 
areas have some level of legal protection. Therefore, we conclude that 
destruction or modification of foraging habitat is not a significant 
threat to van Rossem's gull-billed tern throughout its range now or in 
the foreseeable future.
    The amount of nesting habitat for van Rossem's gull-billed tern is 
more limited. In the United States, nesting habitat in San Diego Bay is 
protected and managed by the San Diego Bay National Wildlife Refuge. 
The population of van Rossem's gull-billed terns in the San Diego Bay 
nesting location has increased since the early 1990s and is now 
expanding to other areas of protected nesting habitat outside of the 
Refuge. At the Salton Sea, the amount and distribution of nesting 
habitat has varied through time with nest sites being lost and added 
with changing conditions (primarily the water level of the Salton Sea, 
but also the availability of manmade impoundments that intentionally or 
accidentally have areas suitable for nesting). Although the continued 
existence of individual nest sites into the foreseeable future is 
unknown, the evidence suggests that, even under changing conditions, it 
is unlikely that all nesting habitat would be lost. Moreover, the Sonny 
Bono Salton Sea National Wildlife Refuge, which has regularly harbored 
several colonies of nesting van Rossem's gull-billed terns, including 
the consistently productive D pond, has been actively managing for the 
benefit of van Rossem's gull-billed tern by creating and maintaining 
areas of nesting habitat, including artificial nesting platforms. 
Although we acknowledge that Salton Sea Refuge may not always be able 
to provide the same type or same level of management every year, its 
record of accomplishment for more than 15 years suggests that continued 
beneficial management will likely continue into the foreseeable future. 
Therefore, we determine that nesting habitat for the Salton Sea 
population of the van Rossem's gull-billed tern is not significantly 
threatened by permanent loss or destruction.
    In Mexico, the available information on nesting habitat is not as 
extensive and is less detailed than U.S. data, but it suggests that 
many nesting habitat areas are located in protected areas and are not 
likely to be destroyed or substantially modified, while other areas are 
subject to loss from habitat destruction or modification. The nest 
sites at Isla Montague, Marismas Nacionales, and Bah[iacute]a Santa 
Mar[iacute]a are located within protected areas. Moreover, the nest 
sites at these nesting locations, along with the nest sites at Isla 
Montague, Laguna Ojo de Liebre, Bah[iacute]a de Ceuta, Laguna del 
Caimanero, and Laguna Potos[iacute], are situated on low islands that 
are subject to flooding during winter storms or high tides; as a 
result, substantial manmade developments on the islands are unlikely. 
The nest sites at Cerro Prieto are dependent on the management of waste 
water at the geothermal generation facility, which is uncertain at this 
time; some van Rossem's gull-billed terns from this nesting location 
may have moved and nested at Isla Montague in 2010 in response to 
changes in the amount of available habitat at Cerro Prieto. Portions of 
Laguna Cuyutl[aacute]n near port operations may be subject to dredging 
activities, which may destroy existing areas of nesting habitat for van 
Rossem's gull-billed terns but may also

[[Page 58664]]

result in the creation of dredge-spoil islands that may serve as 
additional nesting habitat. The portions of Laguna Cuyutl[aacute]n away 
from the port are less likely to be destroyed. Thus, most of the van 
Rossem's gull-billed tern nest sites in Mexico are not likely to be 
substantially destroyed or modified. Moreover, because van Rossem's 
gull-billed terns are resilient and can move from one area of nesting 
habitat to another, the loss of a limited amount of nesting habitat 
will not likely significantly affect the species.
    Based on our review of the best available scientific and commercial 
information, we conclude that van Rossem's gull-billed tern is not 
threatened by the present or threatened destruction, modification, or 
curtailment of its habitat or range now or in the foreseeable future.

Factor B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

    Within the context of this factor, overutilization is the capture 
or collection of individuals of a species, including its eggs or young, 
to an extent (at a high enough rate) that it affects the conservation 
status of the species. We are not aware of any information suggesting 
that adult van Rossem's gull-billed terns are utilized (collected, 
harvested) or will likely be utilized in the foreseeable future for 
commercial, recreational, scientific, or educational purposes anywhere 
in the subspecies' range (but see the ``Intentional Killing'' section 
under Factor E). The information available to us regarding capture or 
collection of eggs or chicks of van Rossem's gull-billed terns in the 
United States indicates that risks to the species from overutilization 
for commercial, recreational, scientific, or educational purposes is 
not a significant threat, and we determine that this factor will not 
become a significant threat to the occurrences of van Rossem's gull-
billed tern in the United States in the foreseeable future.
    In western Mexico, egging, the collection of wild bird eggs by 
people for subsistence or other uses, has occurred historically (for 
example, see Mailliard 1923, pp. 443-456). More recently, egging 
activities at Guerrero Negro in the 1970s, prior to the first known 
nesting of van Rossem's gull-billed terns at this location, was so 
severe that nesting waterbirds were extirpated from several islands 
(Castellanos et al. 2001 p. 367). However, the available information on 
the current impacts of egging or other utilization activities on van 
Rossem's gull-billed tern lacks specificity and is somewhat 
conflicting. Molina et al. (2010, p. 13) stated that this activity is 
not a threat to van Rossem's gull-billed tern and Palacios (2010, p. 
14) states, ``Other than tidal flooding, no evident direct threats were 
documented for this colony.'' However, Palacios and Mellink (2006, p. 
60) noted in a general statement that egging occurred at Isla Montague 
at some unspecified time in the past and postulated that it could occur 
again, but they did not provide specific information on whether egging 
activities had affected or were affecting van Rossem's gull-billed tern 
nests. Thus, the likelihood of this threat affecting the subspecies at 
this nesting location is not clear, but none of the information 
available suggests that utilization occurs or is likely to occur with 
any appreciable frequency.
    Mellink et al. (2009, p. 51) also considered egging as a potential 
threat in Laguna el Potos[iacute], should the colony there be 
discovered by the human inhabitants of the area, but again, the authors 
did not provide specifics on the likelihood of it affecting the 
subspecies. Mu[ntilde]oz del Viejo et al. (2004, p. 196) documented egg 
collection of royal terns (Sterna maxima) at Bah[iacute]a Santa 
Mar[iacute]a, and in the same area they noted that blue-footed booby 
(Sula nebouxii) chicks had been taken by fishermen and used for bait 
(Mu[ntilde]oz del Viejo et al. 2004, p. 196). However, at Bah[iacute]a 
Santa Mar[iacute]a, we have no available information indicating that 
van Rossem's gull-billed terns were targeted for either activity. 
Additionally at this location, Mu[ntilde]oz del Viejo et al. (2004, p. 
199) reported that they successfully worked with the local inhabitants 
to stop this practice, but there are no assurances that such activities 
could not again occur.
    Thus, in Mexico, egging and other forms of utilization have not 
been specifically documented to impact van Rossem's gull-billed tern; 
however, egging has affected, to varying extents, other species of 
birds that can and do nest close to where van Rossem's gull-billed 
terns nest. This suggests egging and other forms of utilization, 
regardless of purpose, are a potential threat to van Rossem's gull-
billed terns. We expect such utilization--should it occur at a van 
Rossem's gull-billed tern nest colony--would result in complete 
reproductive failure for the affected nest colony. However, like a nest 
depredation event, the adult terns would likely survive to nest again 
in the future nesting seasons or, potentially, to renest that same 
season (see Factor C, below, for more details). The available 
information does not suggest that such utilization activities are 
occurring to an extent (at a high enough rate) for it to affect the 
conservation status of the species. Thus, we conclude that 
overutilization for any purpose is not significantly affecting van 
Rossem's gull-billed tern in Mexico at the present time, nor do we 
expect it to be a significant threat in the foreseeable future.
    Therefore, based on our review of the best scientific and 
commercial information available, we conclude that van Rossem's gull-
billed is not threatened by overutilization for commercial, 
recreational, scientific, or educational purposes now or in the 
foreseeable future.

Factor C. Disease or Predation

Disease
    Diseases occur naturally in wildlife populations. The occurrence of 
a disease within the range of a species does not necessarily mean that 
it is deleterious to that species. However, if one or more diseases are 
virulent enough, the conservation status of a species may be affected. 
The susceptibility of van Rossem's gull-billed tern to disease has not 
been well studied, but multiple diseases impacting avian populations 
are present in the areas where van Rossem's gull-billed terns nest. 
Avian botulism, avian cholera, and other diseases have impacted 
thousands of fish-eating birds at the Salton Sea (Friend 2002, pp. 295, 
303), including an outbreak of avian botulism that killed more than 
14,000 birds in the mid-1990s (Roberts 1997, p. 2). Throughout those 
and other disease outbreaks at the Salton Sea, the population of van 
Rossem's gull-billed terns at this location appeared to be unaffected 
(Molina 2004, p. 98; Molina et al. 2010, pp. 14 and 66). This is 
probably because van Rossem's gull-billed terns do not depend solely 
upon fish for food and, at the Salton Sea, they primarily forage for 
crickets (Molina 2009a, p. 1). Because of their diverse foraging 
habits, van Rossem's gull-billed terns appear less likely to be exposed 
to diseases like avian botulism and avian cholera.
    A serious disease threat to avian populations in North America is 
West Nile Virus (WNV). WNV has caused significant declines in bird 
populations since its arrival in the United States in 1999 (LaDeau et 
al. 2007, p. 711). Originally detected in New York, the disease was 
first detected in California in 2003 in the Imperial Valley, and was 
present at the Salton Sea in the late summer of 2003 and in the San 
Diego region by autumn (Reisen et al. 2004, p. 1371). The impact of WNV 
on van Rossem's gull-billed tern, and

[[Page 58665]]

charadriiform waterbirds in general, has not been assessed. 
Charadriiform waterbirds are susceptible to WNV infection, with 
carcasses confirmed positive for WNV in California (Eidson et al. 2001 
p. 617; Komar et al. 2003, p. 313), including a California least tern 
(Sternula antillarum browni) (Foster in litt. 2008). The closest 
related species to van Rossem's gull-billed tern that researchers have 
examined for susceptibility to WNV is the ring-billed gull (Larus 
delawarensis). In a laboratory study, ring-billed gulls showed high 
mortality and viral loads when exposed to WNV (Komar et al. 2003, p. 
313). However, this may not be a good predictor of how van Rossem's 
gull-billed tern might be affected by WNV because variance between 
species in disease response is high (LoGludice et al. 2003, pp. 568-
569), and lab tests of WNV have proven to be undependable predictors of 
conditions in the field (Walker et al. 2007, p. 694). Thus, if van 
Rossem's gull-billed terns were particularly susceptible to WNV or 
other diseases in the wild, we would expect to see a marked decline in 
populations of van Rossem's gull-billed terns that have been exposed to 
the disease, as have been observed in other bird species (LaDeau et al. 
2007, p. 710).
    As noted above, WNV has been present at the two U.S. van Rossem's 
gull-billed tern nesting locations (Salton Sea and San Diego Bay) since 
2003. Although van Rossem's gull-billed tern numbers at the Salton Sea 
have fluctuated over the past decade, their overall population size has 
remained fairly stable since the arrival of WNV to the region (K. 
Molina, in litt. 2010, p. 3). Meanwhile, the San Diego Bay population 
increased over that time (Patton 2009, Table 2). Had van Rossem's gull-
billed tern been substantially affected by WNV, these two populations 
would have shown a decline when the disease arrived in their respective 
regions. The information available shows that these two well-monitored 
populations did not decline. This indicates that the U.S. population of 
van Rossem's gull-billed terns is not significantly threatened by WNV 
now or in the foreseeable future. Further, it suggests that the 
subspecies as a whole is not likely to be substantially affected by the 
disease.
    The amount of information on the prevalence of WNV in western 
Mexico is limited, but there is some indication that the disease has 
been recorded there (Komar and Clark 2006, p. 114). Although the 
population data for van Rossem's gull-billed terns in Mexico is 
limited, there is no indication of marked population decline. 
Nevertheless, as in the United States where evidence of substantial 
effects of the disease on van Rossem's gull-billed tern is lacking, we 
similarly expect no significant effects to populations of the 
subspecies in western Mexico from WNV.
    Unlike other bird species that are sensitive to WNV, such as 
American crow (Corvus brachyrhynchos) and greater sage-grouse 
(Centrocercus urophasianus) that experienced substantial population 
declines from WNV (Reisen et al. 2004, p. 1371; Naugle et al. 2004, p. 
711), the available information shows that populations of van Rossem's 
gull-billed tern have not declined upon exposure to WNV throughout the 
subspecies' range. Moreover, the best available information gives no 
indication that other diseases are substantially affecting the 
subspecies in western Mexico or elsewhere in the subspecies' range.
    Therefore, we conclude that disease, including WNV, is not a 
significant threat to van Rossem's gull-billed tern now, and we have no 
indication that it will be in the foreseeable future.
Predation
    Predation of eggs or flightless young (nest predation) is 
frequently observed at monitored van Rossem's gull-billed tern nest 
sites, but predation of adults is rarely observed (Molina 2000, p. 7; 
2001, p. 8; 2004, p. 96; 2006, p. 7; 2007, p. 11; 2008, p. 189; 2009, 
p. 8; Patton 2002, p. 7; 2006, p. 7; 2008, p. 8; 2009, p. 10; Molina et 
al. 2010, p. 14); thus, we do not consider predation of adults a 
significant threat to the subspecies. The nests of ground-nesting birds 
are particularly susceptible to terrestrial predators, primarily 
mammals (Kruuk 1964, pp. 1-129), although predation from aerial 
predators also occurs (Sears 1979, pp. 202-203). Once a mammalian 
predator discovers or gains access to a nest colony, it typically eats 
all or nearly all eggs or young within the colony, causing that nest 
attempt by the colony to fail. In contrast, avian nest predators 
typically eat only a few eggs or young, causing individual nests to 
fail, but rarely is the entire colony's nesting attempt affected 
(Molina 2007, p. 11). Thus, some level of nest predation is expected to 
occur naturally. Behaviors such as nesting colonially and selecting 
islands and other hard-to-reach places for nesting are, in part, anti-
predator strategies that have evolved as life-history traits in ground-
nesting species (Gochfeld and Burger 1996, p. 628), including van 
Rossem's gull-billed terns. A species' behavior of selecting nest sites 
that would be less likely to be affected by terrestrial predators blurs 
the lines between the Act's five listing factors; that is, a species' 
behavioral strategy to avoid nest predators (which would reduce threat 
of predation under Factor C) is also a consideration in what determines 
the species' nesting habitat (Factor A).
    Another adaptation to nest predation is for birds to renest; that 
is, to nest again in the same breeding season, which typically occurs 
at a different nest site. Although renesting is energetically demanding 
on the adults, it increases the likelihood that a colony will have some 
level of reproduction (productivity) that year. However, the number of 
birds that renest is typically fewer than the number of birds that 
initially nested, and the later in the season a nest is lost, the lower 
the likelihood that a pair will attempt to renest (Thompson et al. 
1997, p. 13), and the later in the season a nest is started, the lower 
the likelihood that nest will successfully fledge young (Massey and 
Atwood 1981, p. 604). Thus, persistent nest predation, despite 
renesting behavior, typically results in reduced annual productivity of 
the nesting colony or even reproductive failure for that colony that 
year. However, as long-lived birds, van Rossem's gull-billed terns do 
not necessarily need to reproduce successfully every year to maintain 
population levels over time.
    Although we have some information on the level of nest predation at 
certain van Rossem's gull-billed tern nesting locations, and we expect 
it to occur at other locations, we do not know how prevalent nest 
predation is rangewide. Of the two nesting locations that are monitored 
regularly (Salton Sea and San Diego Bay), nest predation has been noted 
at nest sites at the Salton Sea, including some that are managed by the 
Sonny Bono Salton Sea National Wildlife Refuge in an effort to reduce 
the likelihood of this threat (Molina 2009b, p. 8). The frequency of 
nest predation by mammalian predators may be increasing at certain nest 
sites at the Salton Sea because the lowering water level of the Sea is 
allowing once-isolated nesting islands to become accessible (Molina 
2009b, p. 8; Molina et al. 2010, p. 13). Of all the van Rossem's gull-
billed tern nest sites at the Salton Sea, nest predation by terrestrial 
predators remains infrequent at only one site, the Sonny Bono Salton 
Sea National Wildlife Refuge headquarters (Rock Hill) ponds, but there 
is much inter-specific competition for nesting and loafing space at 
this site (Molina 2010a, pp. 9-10) (see also the ``Inter-specific Nest-
site Disturbance'' section in Factor E). Nevertheless, van Rossem's 
gull-billed terns are

[[Page 58666]]

successfully fledging young at the Salton Sea (Molina 2006, p. 2; 
Molina 2007, p. 4; Molina 2009b, p. 2) and even in 2010, which had few 
nesting attempts and high nest abandonment for a variety of reasons, 
had some (albeit very few) fledging (Molina 2010a, p. 2). Additionally, 
dropping water levels has allowed other nest sites to become exposed, 
where van Rossem's successfully nested in 2010 (Molina 2010a, p. 2). It 
is unclear whether apparent reduction in nest sites with lower 
likelihoods of being depredated will substantially affect the Salton 
Sea colony of van Rossem's gull-billed terns, but it may translate into 
fewer birds attempting to nest at this location; the remaining may 
potentially move to other nesting locations (e.g., Isla Montague, Cerro 
Prieto, San Diego Bay) instead.
    In contrast, at San Diego Bay, the population of van Rossem's gull-
billed terns has steadily increased in part because active anti-
predator management has limited the amount of nest predation since 1999 
(USFWS 2006, Appendix M, p. 2; Patton 2009, Table 2). The primary nest 
site for van Rossem's gull-billed terns (and other species of colonial, 
ground-nesting waterbirds) in San Diego Bay is rarely substantially 
affected by terrestrial predators because (1) The nests are located on 
an extensive network of dikes where access by terrestrial predators is 
limited by barriers and fences that have been intentionally erected; 
and (2) nonlethal and, if necessary, lethal predator control methods 
are used against those predators that do venture to the nesting areas 
(USFWS 2006, Appendix M).
    Thus, nest predation is not a significant threat at the San Diego 
Bay nesting location because predators are managed to benefit nesting 
colonial waterbirds, including van Rossem's gull-billed terns. Nest 
predation at the Salton Sea is less clear. The available information 
suggests the Salton Sea colony of van Rossem's gull-billed terns is 
being affected by nest predation at some nest sites, but other nest 
sites are productive, including a recently emerged nest site. The 
apparent reduction in the total number of nest sites where nest 
predation is unlikely may mean fewer van Rossem's gull-billed terns 
nest at the Salton Sea in the foreseeable future, but it is unlikely 
that the nesting location will be completely abandoned in the 
foreseeable future. Additionally, even though the Salton Sea is an 
important nesting location, there are other nesting locations for the 
subspecies.
    Because van Rossem's gull-billed terns are long-lived birds that 
are not limited to any particular nesting location, the individual 
adult van Rossem's gull-billed terns that have traditionally nested at 
sites in the Salton Sea area may move to other nesting locations to 
nest. However, such shifts in nesting locations would likely result in 
increased intraspecific competition for nest sites at existing nest 
colonies, the establishment of new nesting locations, or both. As a 
result, some birds may be forced to nest in lower quality habitat where 
they may be subject to increased interspecific competition (Factor E) 
or where the level of nest predation may also be high. It is not clear 
how much of an impact this would have on the conservation status of the 
subspecies because the extent to which birds would have to relocate is 
unclear and reproductive success at existing nesting locations is 
variable from year to year. Thus, although we acknowledge some level of 
impact to the subspecies, the portion of the total population that 
would be affected would be limited, and it would not result in a 
significant threat to the subspecies now or in the foreseeable future.
    In Mexico, nest predation has occurred or was suspected at some 
nest sites (for example, Peresbarbosa and Mellink 2001, p. 267; 
Palacios and Mellink 2007, p. 216). Although information from nest 
sites over multiple years is limited, we have no information to suggest 
that there are sustained, elevated levels of nest predation occurring 
at any of the nesting locations. Some nest sites have been found to be 
inactive in some years (Palacios and Mellink 2007, p. 217). Although 
not atypical for this subspecies, inactivity in some years may indicate 
predation events or other disturbances that have caused nest site 
abandonment, although abandoned or unused nest sites could potentially 
be used again in other years. In some cases, other nesting locations 
are found nearby, suggesting the colony successfully relocated. Thus, 
although nest predation likely occurs in Mexico, it does not appear to 
be at above-normal levels.
    Despite the behaviors that van Rossem's gull-billed terns use to 
reduce the effects of nest predation (e.g., nesting at remote nest 
sites, predatory defense behaviors), it is likely that they, like 
nearly all bird species, suffer some natural level of nest predation. 
We do not know what the natural level of nest predation is for van 
Rossem's gull-billed tern because it varies from nest site to nest site 
and from year to year. Natural and manmade changes may alter the levels 
of nest predation. The level of nest predation appears to be increasing 
at the Salton Sea, and possibly at some sites in Mexico where nest 
sites have shifted. While the shifting of nest sites may indicate 
changes in levels of nest predation, the fact that the colony has moved 
shows that the subspecies can adapt to such changes. Moreover, adult 
van Rossem's gull-billed terns are generally long-lived, which means 
that even if an adult fails to successfully reproduce in a given year, 
it will likely have additional chances to reproduce in the future. 
Therefore, we determine that nest predation at the Salton Sea is not a 
significant threat to the subspecies now or in the foreseeable future. 
Moreover, we determine that this is not a population-limiting factor 
that presents a significant rangewide threat now or in the foreseeable 
future.
Summary of Factor C
    Disease, including avian botulism and WNV, occurs within the range 
of van Rossem's gull-billed tern. In the well-monitored nesting 
locations of San Diego Bay and the Salton Sea, the populations of the 
subspecies are growing or are reasonably stable, despite the presence 
of WNV. Moreover, the Salton Sea population of van Rossem's gull-billed 
terns was not significantly affected by substantial outbreaks of avian 
botulism or avian cholera. Thus, the available information suggests 
that disease is not a significant threat to the subspecies throughout 
its range now or within the foreseeable future.
    Predation of adults is not a significant threat to the subspecies. 
Predation of eggs or young at nest sites (nest predation) is a concern 
for ground-nesting birds such as van Rossem's gull-billed tern. Many 
colonial waterbirds have adapted to this threat by nesting on islands 
and remote areas to reduce the risk of predation or by responding to 
predation events by renesting during the same breeding season. Within 
the United States, nest predation does not appear to pose a significant 
threat to the San Diego Bay van Rossem's gull-billed tern population; 
however, the Salton Sea appears to be experiencing high levels of nest 
predation, at least in some years. While the Salton Sea is an important 
nesting location, the adult van Rossem's gull-billed terns that have 
traditionally nested there are not confined to the Salton Sea and may 
move to other locations to nest. Although such shifts in nesting may 
result in increased use of lower quality habitat, which may result in 
lower reproductive success at those locations, we determine such 
potential impacts

[[Page 58667]]

would not significantly threaten the subspecies because the numbers 
affected and the level of impact are likely to be limited. The level of 
nest predation at nesting locations in Mexico is less clear, but the 
available information suggests that it is not occurring at above-normal 
levels. Therefore, based on our review of the best scientific and 
commercial information available, we conclude that van Rossem's gull-
billed tern is not threatened by disease or predation now or in the 
foreseeable future.

Factor D. The Inadequacy of Existing Regulatory Mechanisms

    The Act requires us to examine the adequacy of existing regulatory 
mechanisms with respect to threats that may place van Rossem's gull-
billed tern in danger of extinction or likely to become so in the 
foreseeable future. Existing regulatory mechanisms that may have an 
effect on potential threats to van Rossem's gull-billed tern can be 
placed into three general categories: (1) U.S. Federal laws, (2) State 
laws, and (3) Mexico Federal laws.
U.S. Federal Laws
Migratory Bird Treaty Act
    The Migratory Bird Treaty Act of 1918 (MBTA) (16 U.S.C. 703-712) 
states that it is unlawful ``to pursue, hunt, take, capture, kill, or 
attempt to take, capture or kill, possess, offer for sale, sell, offer 
to barter, barter, offer to purchase, purchase, deliver for shipment, 
ship, export, import, cause to be shipped, exported, or imported, 
deliver for transportation, transport or cause to be transported, carry 
or cause to be carried, or receive for shipment, transportation, 
carriage, or export, any migratory bird, any part, nest, or eggs of any 
such bird, or any product, whether or not manufactured.'' Mexico is 
also a signatory of the MBTA. Van Rossem's gull-billed tern is included 
in the list of migratory birds internationally protected by the MBTA 
(50 CFR 10.13). The MBTA makes it unlawful to kill or take eggs or 
nests of van Rossem's gull-billed terns, but it does not provide 
protection for habitat.
    As described in the ``Intentional Killing'' section under Factor E, 
below, approximately nine adult van Rossem's gull-billed terns have 
been killed around San Diego Bay under depredation permits issued by 
the Service's Migratory Bird Permit Office, including six killed in the 
early 1990s to protect the federally endangered California least tern 
and threatened western snowy plover, and three killed between 2004 and 
2007 near active airport runways to protect human health and safety. We 
have not issued any other depredation permits for the van Rossem's 
gull-billed tern since the 1990s. The three individual birds 
intentionally killed between 2003 and 2007 represent an insignificant 
number when compared to the overall population (average of 42 nesting 
pairs for this time period, Molina et al. 2010, p. 66) of van Rossem's 
gull-billed terns in San Diego Bay, which increased during that time 
period and has continued to grow since 2007.
National Environmental Policy Act
    All Federal agencies are required to adhere to the National 
Environmental Policy Act (NEPA) of 1970 (42 U.S.C. 4321 et seq.) for 
projects they fund, authorize, or carry out. The Council on 
Environmental Quality's regulations for implementing NEPA (40 CFR parts 
1500-1518) state that agencies shall include a discussion on the 
environmental impacts of the various project alternatives (including 
the proposed action), any adverse environmental effects that cannot be 
avoided, and any irreversible or irretrievable commitments of resources 
involved (40 CFR part 1502). The NEPA itself is a disclosure law, and 
does not require subsequent minimization or mitigation measures by the 
Federal agency involved. Although Federal agencies may include 
conservation measures for gull-billed terns as a result of the NEPA 
process, any such measures are typically voluntary in nature and are 
not required by the statute. Additionally, activities on non-Federal 
lands are subject to NEPA if there is a Federal nexus. NEPA does not 
itself regulate activities that might affect gull-billed terns, but it 
does require full evaluation and disclosure of information regarding 
the effects of contemplated Federal actions on sensitive species and 
their habitats.
Fish and Wildlife Conservation Act
    The Fish and Wildlife Conservation Act of 1980 (16 U.S.C. 2901-
2911) encourages States and Federal departments and agencies to 
conserve and promote conservation of nongame fish and wildlife and 
their habitats. The 1988 amendment to the Fish and Wildlife 
Conservation Act mandates the Service to ``identify species, 
subspecies, and populations of all migratory nongame birds that, 
without additional conservation actions, are likely to become 
candidates for listing under the Endangered Species Act (ESA) of 
1973.'' Our Division of Migratory Bird Management published the Birds 
of Conservation Concern in 2008 (USFWS 2008, pp. 1-87). We identified 
the gull-billed tern (the species as a whole) as a Bird of Conservation 
Concern (see the ``Management Actions'' section above). The species was 
included as a Bird of Conservation Concern both nationally and in 
certain specific Bird Conservation Regions, including the U.S. portions 
of Bird Conservation Regions 32 (Coastal California) and 33 (Sonoran 
and Mojave Deserts) (USFWS 2008, pp. 48 and 49). Because we identified 
the gull-billed tern as a Bird of Conservation Concern, we have denied 
depredation permit requests under the MBTA (USFWS 2010, p. 1) (see 
``Intentional Killing'' section under Factor E).
National Wildlife Refuge System Improvement Act
    The National Wildlife Refuge System Improvement Act of 1997 (Pub. 
L. 105-57) establishes the protection of biodiversity as the primary 
purpose of the national wildlife refuge system. This has led to various 
management actions that have directly benefited van Rossem's gull-
billed tern. For example, at the Sonny Bono Salton Sea National 
Wildlife Refuge, nesting islands and artificial nesting platforms have 
been created and maintained (see Factor A). At the San Diego Bay 
National Wildlife Refuge, predator control has resulted in reduced nest 
predation levels on van Rossem's gulled-billed terns (see Factor C).
U.S. State Laws
    Van Rossem's gull-billed tern is not a listed species under the 
California Endangered Species Act (CESA), the State's primary 
regulatory mechanism to protect species. However, the van Rossem's 
gull-billed tern is considered a bird species of special concern in 
California (Molina 2008, p. 188), an administrative designation that 
carries no formal legal status. According to Comrack et al. (2008, pp. 
1-4), the intent of this designation is to focus attention on animal 
species deemed to be at conservation risk, stimulate research, and 
improve the species' conservation status before they meet California 
Endangered Species Act criteria for listing as a State threatened or 
endangered species. However, impacts to van Rossem's gull-billed tern 
from any projects would require evaluation and disclosure under the 
California Environmental Quality Act (CEQA) (see below) due to its 
consideration as a species of special concern.
    Van Rossem's gull-billed tern also receives protection through the 
State migratory bird provisions of the

[[Page 58668]]

California Fish and Game (CFG) Code. The CFG Code prohibits any take or 
possession of birds that are designated by the MBTA as migratory 
nongame birds, except as allowed by Federal rules and regulations 
promulgated pursuant to the MBTA (Division 4, Part 2, Chapter 1, 
section 3513). Additionally, under the CFG Code, it is unlawful to 
take, possess, or needlessly destroy the nest or eggs of any bird, 
including van Rossem's gull-billed tern, except as otherwise provided 
(Division 4, Part 2, Chapter 1, section 3503). This provides protection 
to van Rossem's gull-billed terns, including their nests, from any 
unlawful take.
California Environmental Quality Act
    The California Environmental Quality Act (CEQA) (Public Resources 
Code 21000-21177) and the CEQA Guidelines (California Code of 
Regulations, Title 14, Division 6, Chapter 3, Sections 15000-15387) 
requires State and local agencies to identify the significant 
environmental impacts of their actions and to avoid or mitigate those 
impacts, if feasible. CEQA applies to projects in California proposed 
to be undertaken or requiring approval by State and local government 
agencies. The lead agency must complete the environmental review 
process required by CEQA, including conducting an Initial Study to 
identify the environmental impacts of the project and determine whether 
the identified impacts are ``significant.'' If significant impacts are 
determined, then an Environmental Impact Report must be prepared to 
provide State and local agencies and the general public with detailed 
information on the potentially significant environmental effects 
(California Environmental Resources Evaluation System, 2010).
    ``Thresholds of Significance'' are comprehensive criteria used to 
define environmentally significant impacts based on quantitative and 
qualitative standards. They include impacts to biological resources 
such as candidate, sensitive, or special status species in local or 
regional plans, policies, or regulations, or by the CDFG or the 
Service; or any riparian habitat or other sensitive natural community 
identified in local or regional plans, policies, regulations or by the 
CDFG or Service (CEQA Handbook, Appendix G, 2010). Defining these 
significance thresholds helps ensure a ``rational basis for 
significance determinations'' and provides support to the final 
determination and appropriate revisions or mitigation actions to a 
project in order to develop a mitigated negative declaration rather 
than an Environmental Impact Report (Governor's Office of Planning and 
Research, 1994, p. 5).
    Section 15380 of the CEQA Guidelines indicates that species 
designated as ``Species of Special Concern'' should be included in an 
analysis of project impacts (Comrack et al. 2008, p. 2). In assigning 
``impact significance'' to populations of unlisted species, factors 
such as population-level effects, proportion of the taxon's range 
affected by a project, regional effects, and impacts to habitat 
features are analyzed. If significant effects are identified, the lead 
agency has the option of requiring mitigation through changes in the 
project or to decide that overriding considerations make mitigation 
infeasible (CEQA section 21002). Protection of listed species through 
CEQA is, therefore, dependent upon the discretion of the lead agency 
involved.
Mexico Federal Laws
    In Mexico, van Rossem's gull-billed tern is protected by what is 
known as the Ecology Law (Ley General del Equilibrio Ecol[oacute]gico y 
la Protecci[oacute]n al Ambiente, or LGEEPA). This law, first enacted 
in 1988 and amended in 1996, is designed to preserve ecosystems and 
allow for sustainable use of biodiversity and development of working 
groups to organize management and protection of the environment in 
designated Natural Protected Areas (Gonzales and Gastelum 2000, p. 50; 
Bezaury-Creel 2005, p. 1031). Although management of protected areas 
has typically been inadequate in Mexico, the situation has been greatly 
improved through the establishment of The National Protected Area 
Commission (Comisi[oacute]n Nacional de [Aacute]reas Naturales 
Protegidas, or CONANP) (Bezaury-Creel 2005, p. 1034). Many management 
plans for protected areas are under development, including one for 
Bah[iacute]a Santa Mar[iacute]a (Bezaury-Creel 2005, pp. 1021, 1034), a 
nesting location for van Rossem's gull-billed terns. However, 
enforcement continues to be problematic in Mexico due to the lack of 
collaboration between different Federal agencies, and between Federal 
and local governments (Fraga and Jesus 2008, p. 21). Furthermore, local 
reserve managers often lack the legal authority to enforce 
environmental laws (Fraga and Jesus 2008, p. 21).
    LGEEPA does not necessarily preserve lands in protected areas; 
instead, areas are considered more as ``multiple use zones'' where 
thresholds are imposed on sustainable use of natural resources to limit 
activities (Bezaury-Creel 2005, pp. 1030-1031). One form of Natural 
Protected Areas, the ``biosphere reserve,'' includes established core 
areas where land alteration is limited (Figueroa and Sanchez-Cordero 
2008, p. 3232). Two of the largest nesting populations of van Rossem's 
gull-billed terns are within biosphere reserves, including Isla 
Montague and Marismas Nacionales. Additionally, the small population of 
van Rossem's gull-billed terns at Laguna Ojo de Liebre, including the 
Guerrero Negro saltworks, is within the El Vizca[iacute]no Biosphere 
Reserve (Palacios 2010, pp. 6 and 16), but the level of protection 
afforded by the reserve is likely limited within the salt production 
facility. Yet LGEEPA, as implemented with the aid of the CONANP, 
provides benefits to van Rossem's gull-billed tern and its habitat, 
benefits the subspecies would not have in the absence of such 
regulatory mechanisms.
Summary of Factor D
    In the United States, the National Wildlife Refuge System 
Improvement Act benefits breeding populations of van Rossem's gull-
billed tern at San Diego Bay National Wildlife Refuge and the Sonny 
Bono Salton Sea National Wildlife Refuge. Additional Federal and State 
regulations provide benefits to the subspecies, through its migratory 
bird status (Federal and State), and to its habitat, through its 
designation as a species of special concern (Federal and State).
    In Mexico, two of the largest nesting populations of van Rossem's 
gull-billed terns are located within biosphere reserves and a third, 
smaller population is in a biosphere reserve where other uses (salt 
production) is occurring. Development is somewhat limited by the 
LGEEPA, especially in core areas of biosphere reserves. The CONANP was 
established to assist in preserving ecosystems and organizing 
management and protection of the environment in these Natural Protected 
Areas. While enforcement continues to be a concern regarding regulatory 
mechanisms in Mexico and active management is lacking in many areas, 
these regulatory mechanisms provide benefits to the van Rossem's gull-
billed tern, benefits that the subspecies would not have otherwise.
    Based on our review of the best scientific and commercial 
information available, we conclude that van Rossem's gull-billed tern 
is not threatened by inadequate regulatory mechanisms now, nor is it 
likely to become so in the foreseeable future.

[[Page 58669]]

Factor E. Other Natural or Manmade Factors Affecting Its Continued 
Existence

Inter-Specific Nest-Site Disturbance
    Van Rossem's gull-billed terns generally nest on small, low islands 
with little or no vegetation. Many other species also use these islands 
for nesting and loafing, where they compete with van Rossem's gull-
billed terns for space; van Rossem's gull-billed terns, especially eggs 
and young, may be inadvertently crushed, injured, or affected by 
agonistic behavior from other species. These interactions, discussed 
below, may affect the productivity of nesting van Rossem's gull-billed 
terns, but such competition is primarily natural, and many colonial, 
ground-nesting species are able to adapt to colonial nesting dynamics.
    Van Rossem's gull-billed terns are known to compete for nesting 
sites with other shorebirds and waterbirds (Molina 2004, p. 98). At San 
Diego Bay and the Salton Sea, territorial behavior between van Rossem's 
gull-billed tern and species such as black skimmer and elegant tern 
result in the loss of van Rossem's gull-billed tern nests on a near-
yearly basis (e.g., see Patton 2009, p. 9). Extent of the damage to the 
colony varies, with approximately 5 to 15 nests (7 to 25 percent of 
total nests) in a colony destroyed (e.g., see Patton 2003, p. 8; 2009, 
p. 9). Territorial disputes between other species in close proximity to 
van Rossem's gull-billed tern colonies can result in temporary 
displacement of adult gull-billed terns from nests. This disturbance 
could result in predation of eggs by gulls and mortality of eggs due to 
high temperatures (Molina 2000, p. 8). Van Rossem's gull-billed terns 
also compete for nesting space at colonies in Mexico, where they share 
most of their breeding sites with black skimmers, Caspian terns 
(Hydroprogne caspia), and laughing gulls (Larus atricilla) (Palacios 
and Mellink 2006, pp. 49-84). At the San Diego Bay nesting colony, van 
Rossem's gull-billed tern chicks have been killed and injured by 
aggressive behavior of black skimmers (Patton 2009, p. 9).
    Competition for space from nonbreeding waterbirds can also cause 
damage to van Rossem's gull-billed tern nests. For example, loafing 
Caspian terns, double-crested cormorants (Phalacrocorax auritus), or 
white and brown pelicans (Pelecanus erythrorhynchos and P. 
occidentalis) have displaced van Rossem's gull-billed terns and 
trampled their eggs, chicks, or both at Salton Sea and San Diego Bay 
(Molina 2001, p. 10; 2007, p. 11; 2009, p. 8; Patton 2001, p. 9, 2009, 
p. 9; Molina et al. 2010, p. 15). These larger birds often use the same 
loafing sites repeatedly, returning after foraging or as nighttime 
roosts. The severity of van Rossem's gull-billed tern displacement and 
egg trampling is dependent on the extent of the use by other birds at a 
particular colony. The presence of larger birds at a colony site for a 
week or less may result in a reduction in van Rossem's gull-billed tern 
nesting success through displacement, egg trampling, or damage of 
individual nests. If their presence continues over a period of weeks, 
van Rossem's gull-billed terns may abandon the colony (Molina 2007, p. 
11). Additionally, nesting van Rossem's gull-billed terns occasionally 
have to compete for space with other species of wildlife. For example, 
at Laguna Cuyutl[aacute]n, eggs of colonial-nesting birds were crushed 
by an American crocodile (Crocodylus acutus) when it crawled onto a 
nesting island (Palacios and Mellink 2007, p. 220).
    Inter-specific interactions often occur naturally at colonies of 
ground-nesting birds. As discussed in the ``Biology'' section above, 
van Rossem's gull-billed terns often adapt to such interactions by 
renesting at the same or other nearby nest sites after disturbances. 
Although the productivity of an affected nest colony of van Rossem's 
gull-billed terns may be reduced or prevented in a given year if such 
disturbances occur repeatedly, it is unlikely that a substantial 
proportion of nesting locations will be significantly affected 
repeatedly from year to year. Therefore, we do not expect any 
deleterious effects associated with these events to be a significant 
threat to van Rossem's gull-billed tern.
Anthropogenic Nest-Site Disturbance
    Colonial nesting waterbirds are sensitive to disturbance from the 
actions of humans and domesticated animals (Sears 1978, p. 9; Safina 
and Burger 1983, p. 168, Blanc et al. 2006, p. 122). Disturbance of 
colonies can cause mortality of eggs and chicks due to increased 
predation and heat stress (Safina and Burger 1983, p. 169). Gull-billed 
terns may be especially sensitive to the presence of humans and animals 
in their nesting colonies and prolonged disturbance can result in 
decreased breeding success (Clapp et al. 1983, p. 348, Molina 2008, p. 
190). Excessive human disturbance at a particular nest site may cause 
van Rossem's gull-billed terns to abandon the nesting attempt at a 
given site in a given year, though in some cases such abandonment 
results in renesting at a different nearby site. Abandonment is not 
necessarily permanent; van Rossem's gull-billed terns may again use 
those nest sites in subsequent years, if the sites are available. 
However, as noted in the ``Predation'' section under Factor C, 
persistent renesting typically results in reduced annual productivity 
for that colony because fewer pairs are subsequently likely to renest 
and those that do are less likely to successfully fledge young (Massey 
and Atwood 1981, p. 604; Thompson et al. 1997, p. 13).
    In the United States, most van Rossem's gull-billed tern nesting 
areas occur in areas that are managed for the benefit of wildlife 
species, including van Rossem's gull-billed terns and other colonial 
nesting waterbirds, which limits the level of human disturbance. 
However, because nesting occurs at different sites within and between 
years, including nest sites located outside of protected or managed 
areas, the subspecies is subject to disturbance in some areas. For 
example, regular visits from boaters and fishermen on Mullet Island in 
the Salton Sea may have caused van Rossem's gull-billed terns to move 
from that nest site (Molina 2001, p. 14). Also at the Salton Sea, lower 
water levels have allowed some nesting islands to become reconnected to 
the mainland, and feral dogs have intruded onto an area used by van 
Rossem's gull-billed tern for nesting, causing the colony to 
permanently abandon this nest site (Molina 2000, p. 7). Similarly, nest 
sites in San Diego Bay have been disturbed in the past (Patton 2001, p. 
9), but predator management actions, including fencing, at this site 
have decreased the incidence of such disturbances (USFWS 2006, pp. 1-
36). Researchers may cause disturbance of nesting birds, though 
monitors and researchers typically conduct their activities in such a 
way as to disturb the population as little as possible (Patton 2009, 
pp. 4-5). Nonetheless, Palacios and Mellink (2007, p. 216) suspected 
that researcher activity may have been a disturbance at some nest sites 
in Mexico, but this appears to have been events associated with 
individual studies and not from monitoring, which involves repeated 
visits within and between years. Therefore, we do not anticipate this 
to be an ongoing, significant threat.
    In Mexico, many nest sites are protected from human disturbance by 
beneficial or benign land uses, or because the nest sites are not 
easily accessed by humans (Molina and Garrett 2001, p. 27; Palacios and 
Mellink 2006, pp. 71, 78), such as at the Guerrero Negro saltworks 
(Palacios and Mellink 2007, p. 217). However, human disturbance has 
been noted near van

[[Page 58670]]

Rossem's gull-billed tern nest sites, including two of Mexico's largest 
colonies, Laguna Pericos (in Marismas Nacionales) and Isla Montague, 
plus also Laguna del Caimanero and Laguna Cuyatl[aacute]n (Palacios and 
Mellink 2006, pp. 60, 67, 74 and 78). Additionally, Estero 
Teacap[aacute]n (in Marismas Nacionales), unlike most other nest sites 
in Mexico, is often visited by tourists (Palacios and Mellink 2006, p. 
71). Available information on disturbance at nest sites in Mexico is 
limited to those data that were generated by only one or two visits, 
which limits our ability to determine the frequency of past 
disturbances or the likelihood that such disturbances will continue 
into the foreseeable future. However, frequent disturbance (among 
others) would likely result in van Rossem's gull-billed terns 
abandoning nest sites. At Isla Montague, a site for which we have 
intermittent data since 1992, nesting has continued at roughly the same 
levels despite the apparent disturbances over that time (Palacios and 
Mellink 1992, p. 43). Similarly, in a qualitative assessment of the 
terns' reaction to the presence of fishermen, Palacios and Mellink 
(2006, p. 67) note that van Rossem's gull-billed terns at Laguna del 
Caimanero appeared to become ``habituated'' to human disturbance and 
continued to nest despite the presence of people. Thus, the limited 
information available to us does not indicate that there is a long-term 
population-level threat associated with manmade nest disturbance to the 
van Rossem's gull-billed tern now or in the foreseeable future.
Intentional Killing
    Human-related actions that result in the death of individual van 
Rossem's gull-billed terns have the potential to affect the continuing 
existence of the species if the number of individuals killed 
substantially affects the mortality rate of the subspecies. The 
mortality rate in a population may substantially affect a population if 
it continually exceeds the rate of increase (or birth rate) (Thomas 
1994). Intentional killing activities may include take authorized under 
existing laws or unauthorized depredation. Because either action, by 
definition, results in the death of individual van Rossem's gull-billed 
terns (or, in certain cases, destruction of eggs) we assess these 
potential actions in this section; however, we note that the motives 
and level of oversight differ between the two categories. Below we 
assess the effects of intentional killing of van Rossem's gull-billed 
terns as a potential threat to the subspecies.
    In the San Diego Bay region, three van Rossem's gull-billed terns 
have been intentionally killed as part of the U.S. Navy's Bird/Animal 
Aircraft Strike Hazard (BASH) program. The Navy deemed it necessary to 
kill three adult van Rossem's gull-billed terns near active runways for 
human safety reasons, two in 2004 on Naval Base Coronado and one in 
2007 at Naval Outlying Landing Field, Imperial Beach (Molina et al. 
2010, p. 16). The Service authorized these removals under a migratory 
bird depredation permit for airport operations pursuant to the 
Migratory Bird Treaty Act (50 CFR part 21). The three van Rossem's 
gull-billed terns killed under the Navy's BASH program have been the 
only individuals intentionally killed under this program since the 
subspecies established a nesting colony in San Diego Bay in 1987.
    Additionally, six (or possibly seven) adult van Rossem's gull-
billed terns were killed between 1993 and 1995 in San Diego because 
they were considered potential threats to federally endangered 
California least terns and federally threatened western snowy plovers 
(Patton 2002, in litt., p. 1; Molina et al. 2010, p. 15). These two 
species nest in highly managed areas in the San Diego Bay region, and 
management measures include limiting the effects of predators on listed 
species. Depredation of California least tern chicks and western snowy 
plover chicks by van Rossem's gull-billed terns has increased as the 
van Rossem's gull-billed tern population has increased in San Diego Bay 
(Patton 2009, Appendix C; Marschalek 2010, pp. 12-13, 20). Since 1995, 
only nonlethal methods have been used by local managers in what have 
largely been unsuccessful attempts to dissuade van Rossem's gull-billed 
terns from depredating the chicks of California least terns and western 
snowy plovers. The Navy does not currently have authorization from the 
Service to use limited lethal control of van Rossem's gull-billed terns 
in areas the Navy manages to benefit California least terns and western 
snowy plovers.
    As the level of depredation of California least terns and western 
snowy plovers by van Rossem's gull-billed terns has increased in the 
San Diego Bay region, local land managers have considered methods other 
than direct lethal control of adults to reduce the impact of van 
Rossem's gull-billed terns on the other listed species. For example, as 
published in a draft Environmental Assessment under the National 
Environmental Policy Act, we proposed in an experiment at the San Diego 
Bay National Wildlife Refuge to gather data that would help us answer 
the following management questions: (1) Could we reduce the loss of 
California least tern and western snowy plover chicks to predation by 
van Rossem's gull-billed terns in the vicinity of San Diego Bay by 
lowering the productivity within the van Rossem's gull-billed tern 
colony at San Diego Bay; and (2) could productivity within the van 
Rossem's gull-billed tern colony at San Diego Bay be reduced without 
causing significant direct impacts to San Diego Bay's breeding 
population of adult van Rossem's gull-billed terns (USFWS 2009, p. 4). 
In part, the experiment proposed to addle eggs of van Rossem's gull-
billed terns nesting at the San Diego Bay National Wildlife Refuge to 
determine if population size of van Rossem's gull-billed terns in San 
Diego Bay could be controlled while avoiding a decline of the overall 
population of van Rossem's gull-billed terns (USFWS 2009, pp. 8-9). 
Although initially proposed for the 2009 nesting season, no further 
action on the proposed project was taken. No additional compliance with 
the National Environmental Policy Act was prepared related to the 
proposed project, and we are not planning to implement this proposed 
project now or in the foreseeable future.
    The killing of van Rossem's gull-billed terns as predator control 
has only occurred in San Diego Bay, and no van Rossem's gull-billed 
terns have been killed there for predator control since 1995. We are 
not aware of any killing of van Rossem's gull-billed terns as BASH 
management anywhere except San Diego Bay, and only three individuals 
were killed there, two in 2004 and one in 2007. The population of van 
Rossem's gull-billed terns remains in the San Diego Bay area and has 
consistently grown since 1999 (Patton 2009, Figure 1, no page number). 
Given the continued level of growth of the San Diego Bay population of 
van Rossem's gull-billed terns over the same time period as the three 
individuals were killed under the BASH program, the level of take under 
this program has not significantly affected the San Diego Bay 
population of van Rossem's gull-billed terns, or the subspecies 
rangewide. Thus, lethal control of van Rossem's gull-billed terns for 
predator control and BASH prevention is currently not a significant 
threat to the subspecies throughout its range and, because we do not 
anticipate an increase in the lethal control measure associated with 
the Navy's BASH program, this is not a significant threat to the 
subspecies in the foreseeable future.
    In Mexico, van Rossem's gull-billed terns forage at commercial 
shrimp aquaculture farms. Although lethal

[[Page 58671]]

control (e.g., shooting) of predators is not legally authorized in 
Mexico, it has been documented at some of these aquacultural operations 
(e.g., Palacios and Mellink 2006, p. 60). Information on whether this 
activity is widespread is limited. DeWalt (2000, p. 47) implied that it 
occurs more often than it is reported. Molina and Erwin (2006, p. 287) 
suggested that such activities are widespread in Mexico during times 
when shrimp are being harvested. Evidence of lethal control of van 
Rossem's gull-billed terns in Mexico is circumstantial (e.g., Molina 
and Erwin 2006, p. 287; Molina et al. 2010, p. 16), and we are not 
aware of any direct reports of van Rossem's gull-billed terns being 
shot or otherwise killed at shrimp ponds within its range. Some van 
Rossem's gull-billed terns may be killed in this manner; however, given 
the lack of evidence of lethal control of van Rossem's gull-billed 
terns at aquacultural ponds, we conclude that the practice does not 
occur frequently enough to negatively affect the status of the 
subspecies. We have no information to suggest this will change in the 
foreseeable future. Therefore, the use of lethal control at 
aquacultural ponds is not a significant threat to van Rossem's gull-
billed tern now nor is anticipated to be a significant threat in the 
foreseeable future.
Contaminants
    High levels of pesticides and heavy metals are known to cause 
reproductive harm in breeding birds (Longcore et al. 1971, p. 486; King 
et al. 1978, p. 17). The organochlorine pesticide known as DDT breaks 
down in the environment to form DDE, which may cause thinning of 
eggshells and decreased reproductive success in birds (Longcore et al. 
1971, pp. 486, 489). Although DDT was banned in the United States in 
the 1970s, it was used for malarial control in Mexico until the early 
1990s (Garc[iacute]a-Hern[aacute]ndez et al. 2006, p. 1640). Coastal 
lagoons in Mexico have widely varying levels of pesticides 
(P[aacute]ez-Osuna et al. 2002, p. 1305), with DDE found in elevated 
levels in some lagoons that contain nesting sites for van Rossem's 
gull-billed terns (Galindo et al. 1997, p. 1076; Garc[iacute]a-
Hern[aacute]ndez et al. 2001, p. 90; Carvalho et al. 2002, p. 1262). 
Additionally, selenium is a naturally occurring element that may also 
act as a contaminant and affect birds under certain conditions. At low 
levels, selenium is an essential trace nutrient that serves multiple 
metabolic functions in animals (Arthur and Beckett 1994, p. 620), but 
at higher concentrations it can cause embryo malformation and death 
(Hoffman et al. 1988, p. 521). The available information indicates that 
levels of selenium are elevated within sediments at the Salton Sea 
(Miles et al. 2009, p. 2) and along the Colorado River channel close to 
the Isla Montague nesting location (Garc[iacute]a-Hern[aacute]ndez et 
al. 2001, pp. 72 and 73), but at levels below thresholds known to cause 
reproductive harm at Cerro Prieto (Garc[iacute]a-Hern[aacute]ndez et 
al. 2001, pp. 72 and 73).
    Birds accrue contaminants mainly through the food they eat, with 
fish-eating birds commonly accumulating higher levels of contaminants 
than birds that feed on seeds or invertebrates (Frank et al. 1975, p. 
214, Focardi 1988, p. 253, Ruelas-Inzunza et al. 2009, p. 418). For 
example, past studies have linked reproductive failure with heightened 
pesticide levels in the common tern (Sterna hirundo) and the roseate 
tern (Sterna dougallii), both fish-eating species (Hays and Risebrough 
1972, p. 21; Fox 1976, p. 470), but are less pronounced in the black 
tern (Chlidonias niger), which is primarily insectivorous (Frank et al. 
1975, pp. 211, 214). Although the diet of van Rossem's gull-billed 
terns may include fish, they typically eat a variety of prey items, 
with high percentages of invertebrates (Erwin et al. 1998a, p. 325). 
For example, at both Salton Sea and San Diego Bay, van Rossem's gull-
billed terns primarily forage on invertebrates, with fish composing 
only about a quarter of their diet (Molina and Marschalek 2003, p. 23; 
Molina 2009a, p. 10). While van Rossem's gull-billed terns are known to 
prey on small chicks of other bird species, this prey item makes up the 
smallest portion of their diets (Molina et al. 2010, p. 7).
    Although few studies have measured effects of contaminants on van 
Rossem's gull-billed tern, the available information from a small 
number of samples, as summarized in Molina et al. (2010, p. 15), found 
elevated levels of total DDT from one van Rossem's gull-billed tern egg 
from San Diego Bay, but this concentration was still below the 
thresholds found to be harmful in other species. Other contaminants, 
such as selenium (from eggs collected at Salton Sea), arsenic, cadmium, 
copper, mercury, nickel, and zinc (from one San Diego egg), were all 
found to be at concentrations below threshold levels (Molina et al. 
2010, p. 15). Based on this best available information, we do not 
consider contaminants to be a significant threat to the van Rossem's 
gull-billed tern now or in the foreseeable future.
Food Availability
    During periods when the subspecies is not nesting, including 
migration and while wintering, van Rossem's gull-billed terns, as 
highly mobile birds, can cover wide areas to search for food. In 
contrast, food availability near nesting sites is critical for 
successfully raising young. However, the availability of food (prey 
items) is naturally variable. Moreover, unlike other tern species that 
are dependent on fish as their sole food source, van Rossem's gull-
billed terns opportunistically eat a variety of prey items found over a 
range of aquatic and terrestrial areas (Parnell et al. 1995, p. 1; 
Gochfeld and Burger 1996, p. 645). It is unlikely that all potential 
prey items for van Rossem's gull-billed tern will be affected at the 
same time, and this subspecies is able to refocus its foraging behavior 
to locate alternate sources of prey. If the overall availability of 
prey items is low during a given year in breeding areas, it will likely 
result in the reduction or loss of productivity for that year.
    However, the adult van Rossem's gull-billed terns would likely 
survive because they are highly mobile and can find food elsewhere, 
even if it means abandoning the nesting attempt and flying to other 
nesting or foraging locations within the subspecies' range. 
Additionally, because van Rossem's gull-billed terns are long-lived, 
most individual adults will survive to nest the following year--at the 
original nesting location, or perhaps even moving to a different 
nesting location. For example, evidence suggests van Rossem's gull-
billed terns regularly move between the Salton Sea, Cerro Prieto, Isla 
Montague, and San Diego Bay nesting locations within or between years, 
although food availability is not suspected as the motivation for such 
relocations (Molina and Garrett 2001, p. 26; Patton 2001, p. 8; Molina 
2004, p. 98; Palacios 2010, p. 12 and 15). Thus, we do not consider a 
lack of food availability to be a significant threat to the subspecies 
now or in the foreseeable future.
Small Population Size
    Small populations are disproportionately affected by demographic, 
genetic, and environmental stochastic (random) events, and natural 
catastrophes (Caughley 1994, pp. 217-227; Asquith 2001, pp. 345-352). 
Genetic stochastic events can further influence population demographics 
through inbreeding depression and genetic drift (Lande 1988, pp. 624-
635; Whitlock and B[uuml]rger 2004, pp. 155-170). The point at which

[[Page 58672]]

a population becomes a ``small population'' is not clear and varies by 
species-specific or situational-specific factors. Moreover, there is 
disagreement among scientists and considerable uncertainty as to the 
population size adequate for long-term persistence of wildlife 
populations. There is, however, agreement that population viability for 
species of vertebrates (including birds) is more likely to be ensured 
if population sizes (typically breeding adults) are in the thousands of 
individuals rather than hundreds (Traill et al., 2010, p. 32; Reed et 
al. 2003, p. 30, Table 3). However, as stated by Thomas (1990, p. 324), 
``there is no `magic' population size that guarantees the persistence 
of animal populations.'' Moreover, the amount of time that most authors 
consider to be ``long term'' is many decades or even centuries (for 
example, see Shaffer 1981, p. 132; Soul[eacute] and Simberloff 1986, p. 
28; Traill et al. 2010, p. 31; see also Reed et al. 2003, p. 30, Table 
3 therein).
    Thus, we do not consider rarity alone to meet the information 
threshold indicating that the species may warrant listing. In the 
absence of information identifying threats to the species and linking 
those threats to the rarity of the species, the Service does not 
consider rarity or small populations alone to be a threat. A species 
that has always had small population sizes or been rare, yet continues 
to survive, could be well equipped to continue to exist into the 
future. Many naturally rare species have persisted for long periods 
within small geographic areas, and many naturally rare species exhibit 
traits that allow them to persist despite their small population sizes. 
Consequently, the fact that a species is rare or has small populations 
does not necessarily indicate that it may be in danger of extinction 
now or in the foreseeable future.
    Although surveys were conducted through much of the subspecies' 
breeding range in 2010, the surveys were conducted fairly late in the 
nesting season, and, thus, the most complete (best available) estimated 
breeding population size of van Rossem's gull-billed tern is from the 
2003 to 2005 period at approximately 800 pairs of adults rangewide. 
That translates to approximately 1,600 individual adults. This rough 
estimate of population size is largely based on counts of adults at 
nesting locations; as such, this figure approximates the number of 
breeding adults but does not include nonbreeding individuals. However, 
as discussed in the ``Population Size'' section, the data we have 
suggests the overall population of this subspecies has never been 
particularly large. Although Pemberton (1927, p. 256) estimated that 
there were about 500 pairs (1,000 individuals) at the Salton Sea in 
1927, there are no estimates of population sizes from any other 
location in western North America within that timeframe.
    The Salton Sea now supports roughly 100 to 200 pairs (200 to 400 
individuals); thus, the Salton Sea population has decreased since the 
1920s. However, the Salton Sea (or Lake Cahuilla) has existed only 
intermittently through recent history and prehistory, which means that 
over time it has not served as a persistent and consistent nesting 
location. The available historical information suggests that the 
population of the subspecies in Mexico has been small since at least 
the early 1900s. Additionally, many of the places that van Rossem's 
gull-billed terns nest currently were not occupied historically, 
including San Diego Bay, Laguna Ojo de Liebre (Guerrero Negro 
saltworks), and Cerro Prieto geothermal plant (which opened in 1973), 
suggesting the breeding range of the subspecies has expanded recently. 
However, we lack the information to determine if these additional 
nesting sites are the result of an actual increase in total population 
or just a redistribution of the breeding population.
    Additionally, inbreeding depression and genetic drift are less 
likely in a subspecies in which individuals regularly move between and 
among other nesting locations, allowing opportunities for genetic 
mixing. Also, the wide geographic range over which the subspecies 
breeds suggests that it would be unlikely that all van Rossem's gull-
billed tern nesting locations would be simultaneously affected by a 
catastrophic environmental event (such as a drought, flood, or extreme 
weather). Even if a large storm event, such as a hurricane, during the 
breeding season were to move through the northern end of the Gulf of 
California to the Salton Sea area, where several large nesting 
populations occur (Table 1, Figure 1), it may have an effect on the 
subspecies' reproductive efforts for that year; however, it is unlikely 
to result in the death of a significant number of adult van Rossem's 
gull-billed terns because they are capable flyers. Therefore, although 
the small population size may possibly be cause for concern, threats 
associated with small population sizes (i.e., demographic or genetic 
bottlenecks, inbreeding depression, genetic drift, and catastrophic 
events) are not significantly affecting van Rossem's gull-billed tern 
and they are not likely to affect the subspecies in the foreseeable 
future.
Climate Change
    Direct observations of recent climate change include increases in 
global average air and ocean temperatures, widespread melting of snow 
and ice, and rising global average sea levels, and provide unequivocal 
evidence for global warming of the Earth's climate system 
(Intergovernmental Panel on Climate Change or IPCC 2007, p. 5). These 
changes in climate are expected to have an effect on many ecosystems; 
however, wetlands are likely to be particularly affected given their 
sensitivity to changes in precipitation and evapotranspiration (MacIean 
et al. 2007, p. 12). However, there is little specific information 
available that directly pertains to the likely effects of anthropogenic 
global climate change on van Rossem's gull-billed tern. Below, we 
summarize the applicable information.
    Climate change-related impacts were recently evaluated for the San 
Diego region, which includes the San Diego Bay van Rossem's gull-billed 
tern nesting location, in a paper prepared by the California Energy 
Commission's Public Interest Energy Research Program's California 
Climate Change Center (CCCC). This paper used three climate models and 
two greenhouse gas emissions scenarios (A2 and B1, from the IPCC 2007, 
p. 18) to develop downscaled global predictions for climate change 
impacts to the San Diego region by 2050. The report concluded that 
temperatures for San Diego County would increase 1.5 [deg]F to 4.5 
[deg]F (0.8 [deg]C to 2.5 [deg]C), but warming along the coast was 
likely to be more moderate than inland locations (approximately 50 km 
(30 mi) inland) due to the influence of the Pacific Ocean (CCCC 2009, 
p. 12). However, it is not clear whether or how much this will affect 
van Rossem's gull-billed terns that nest at the San Diego Bay nesting 
location. We did locate one published study addressing climate change 
and the phenology (the timing of climate-related annual patterns in 
wildlife) of migration for the ``eastern'' subspecies of gull-billed 
tern and other summer- and winter-resident coastal birds along the 
Texas coast (Foster et al. 2010). In this study, the authors found that 
(warming) temperatures did not have a direct effect on migration 
phenology of ``eastern'' gull-billed terns at this location, but they 
speculated that it might be important at other places or times along 
migration routes (Foster et al. 2010, p. 122). Thus, at least for 
``eastern'' gull-billed tern at this study site, increasing average 
temperature appeared to have little effect on

[[Page 58673]]

migration phenology. Therefore, this study does not provide evidence to 
support a premise that climate change is a significant threat to van 
Rossem's gull-billed tern.
    We are not aware of similar downscaled regional climate models for 
the inland van Rossem's gull-billed tern nesting locations, but as 
suggested above, inland temperatures are expected to rise. The region 
containing the Salton Sea and Cerro Prieto nesting locations is very 
hot during the nesting season. Eggs left unattended during the heat of 
the day in this environment can exceed 50 [deg]C (122 [deg]F), some 5 
to 10 degrees hotter than the temperature range for embryo development 
(Grant 1982, pp. 56 and 60). Thus, even under current temperature 
regimes, ground-nesting birds in this region must attentively cool 
their eggs during the day. Van Rossem's gull-billed terns soak their 
belly feathers in water and use other techniques to cool their eggs 
(and themselves) when daytime temperatures peak (Grant 1982, p. 39). We 
do not know the maximum temperature the subspecies can endure while 
nesting; however, it is clear that the subspecies has natural 
behavioral adaptations to keep its eggs within an acceptable 
temperature range for development in very hot environments. Because the 
remaining nesting locations are coastal--and thus the existing 
temperatures are milder and the potential temperature increases are 
more likely to be moderate--increasing temperatures associated with 
global climate change is not likely to be a significant threat to the 
subspecies.
    Additionally, in the CCCC study, future precipitation projections 
for this region were mixed, with three simulations indicating drier 
conditions and three simulations indicating wetter conditions; however, 
all agreed on a high degree of variability of annual precipitation, 
which the authors suggest as indicating high likelihood of drought 
(CCCC 2009, p. 13). Substantial changes in the amount of precipitation 
could potentially affect terrestrial prey availability for van Rossem's 
gull-billed tern in the San Diego region, but because the modeled 
forecasts were inconclusive, there is little evidence to suggest that 
van Rossem's gull-billed terns in the San Diego Bay region would be 
significantly affected. Moreover, van Rossem's gull-billed terns in the 
San Diego Bay region can and often do forage on marine prey and prey 
items that depend on marine systems, which are less likely to be 
substantially affected by changes in precipitation (Molina and 
Marschalek 2003, p. 8 and Figure 8). Similarly, changes in 
precipitation (increase or decrease) are not likely to affect van 
Rossem's gull-billed tern at the other coastal nesting locations.
    However, prolonged drought could potentially affect the amount of 
water in the Colorado River (Karl et al. 2009, p. 130), which is the 
source of irrigation water for agricultural fields near the Salton Sea 
and Cerro Prieto nesting locations. If agriculture is severely 
curtailed in this region, the amount of food available to van Rossem's 
gull-billed terns will likely be substantially affected. A drought of 
that magnitude would also likely impact the amount of water available 
for maintaining nest sites at the Salton Sea. Even if a severe drought 
resulted in the loss of nesting habitat at the Salton Sea and Cerro 
Prieto, adult van Rossem's gull-billed terns would likely move to other 
nesting locations.
    Further, three simulation scenarios in the CCCC study were used to 
model sea level rise for the San Diego region and results indicate an 
increase in sea level of 12 to 18 inches (30 to 46 centimeters) by 2050 
(CCCC 2009, p. 14). The study also looked at the effects of sea level 
rise in combination with wave activity for six already flood-prone 
areas in San Diego County, estimating sea level with both tide and wave 
run-up elevation recurrences (CCCC 2009, pp. 14-18). South San Diego 
Bay, the current nesting location of the van Rossem's gull-billed tern 
population, was not included in the results; however, coastal areas 
from South Imperial Beach to Oceanside Beach were evaluated (CCCC 2009, 
pp. 16-18). Tidal fluctuations alone were found to inundate sandy 
beaches in many areas, including the Tijuana River mouth (CCCC 2009, p. 
16), and incorporating a moderately common frequency of wave events for 
this location resulted in flooding of most of the sandy beaches here 
and in other coastal areas in San Diego County (CCCC 2009, p. 16).
    However, in south San Diego Bay, van Rossem's gull-billed terns 
predominantly nest on certain artificial dikes within a network of 
dikes that form salt evaporation ponds (saltworks) (USFWS 2006, p. 3-
67; Patton 2009, Summary [no page number]). The nesting dikes are 
within the outer perimeter of the saltworks, which means they are not 
directly exposed to the tidal waters of San Diego Bay, and the dikes in 
the saltworks range from about 3 to 8 feet (1 to 2.5 meters) above the 
water level (USFWS 2006, p. 3-64). Although the San Diego Bay National 
Wildlife Refuge is considering several potential alternatives for 
managing south San Diego Bay in the future, they all include 
maintaining colonial waterbird nest sites, including for van Rossem's 
gull-billed tern (USFWS 2006, pp. 2-47 to 2-107). Therefore, we do not 
expect sea-level rise associated with anthropogenic climate change to 
be a significant threat to van Rossem's gull-billed tern in San Diego 
Bay.
    While we lack information regarding the specifics of the saltworks 
nest sites in Mexico, it seems reasonable to assume that the nest sites 
at these locations will be similarly insulated from sea-level rise by a 
system of dikes that will be maintained for salt production. Inland 
nesting locations in Mexico (Cerro Prieto) and the United States (the 
Salton Sea) are also not threatened by sea-level rise resulting from 
climate change. Additionally, coastal areas of Mexico generally do not 
face the same magnitude of ``coastal squeeze'' scenarios that are 
predicted to occur with sea-level rise in coastal California because 
coastlines in Mexico are not as developed and new nest sites and 
foraging areas may be created as coastline migrates inland and current 
upland areas are converted to saltmarsh or intertidal flats (Galbraith 
et al. 2002, p. 177). Therefore, despite a high level of uncertainty, 
we do not expect sea-level rise associated with anthropogenic climate 
change to be a significant threat to van Rossem's gull-billed tern 
throughout the subspecies' range now or in the foreseeable future.
    Other available information on the potential effects of 
anthropogenic global climate change on van Rossem's gull-billed tern 
includes a vulnerability assessment for migratory waterbirds within the 
African-Eurasian Flyway (MacIean et al. 2007, pp. 1-100). This 
assessment found a ``minimal threat from climate change'' for the gull-
billed tern (MacIean et al. 2007, p. 84), which, by range, would be 
referring to the nominate subspecies (Gelochelidon n. nilotica) 
(Gochfeld and Burger 1996, p. 645). However, the methodologies used by 
MacIean et al. (2007, pp. 1-100) were not appropriate to our status 
assessment of van Rossem's gull-billed tern because the criteria and 
score levels they used were largely subjectively determined and did not 
translate well to our threats-based assessment under the Act. 
Therefore, this study does not provide evidence to support a premise 
that climate change is a significant threat to van Rossem's gull-billed 
tern.
    While we recognize that climate change is an important issue with 
potential effects to listed species and their habitats, we lack 
adequate information to make precise oceanographic and atmospheric 
predictions regarding its effects to van Rossem's gull-billed tern, its 
prey, or its

[[Page 58674]]

habitat. However, based on our review and evaluation of the best 
currently available data, we determine that the potential direct 
effects of predicted climate change on the subspecies is not a 
significant threat to the van Rossem's gull-billed tern now or in the 
foreseeable future.
Summary of Factor E
    We identified that both inter-specific and manmade nest site 
disturbance may have an effect on the productivity of van Rossem's 
gull-billed terns. However, their ability to relocate and renest 
following disturbance combined with the minimal amount of human 
disturbance to nest sites in both Mexico and the United States 
indicates that nest site disturbance is not a significant threat to the 
subspecies now or within the foreseeable future.
    Intentional killing of van Rossem's gull-billed terns has been very 
limited in the past and currently only occurs for human safety reasons 
in the United States. There is no indication that it will increase in 
the future. Illegal killing of birds at aquaculture facilities in 
Mexico has been observed but the extent to which it occurs and what 
effect this may have on the subspecies is not known. Although it is 
likely to occur at some level, the lack of documentation that van 
Rossem's gull-billed terns are affected by this practice suggests that 
it does not occur frequently. Thus, intentional killing is not a 
significant threat to the subspecies throughout its range, nor is it 
likely to become a significant threat within the foreseeable future.
    Contaminants, particularly DDT/DDE and selenium, can negatively 
affect bird species including van Rossem's gull-billed tern and have 
been found at elevated levels at certain nesting locations, although 
very little data are available with respect to van Rossem's gull-billed 
terns and their nest sites. Based on the locations for which we have 
information, contaminant levels were below known thresholds for other 
species. Moreover, van Rossem's gull-billed terns are less likely to be 
exposed to high levels of contaminants because they eat a variety of 
foods, including invertebrates, and contaminants levels are less 
concentrated in invertebrates. Therefore, contaminants are not likely a 
significant threat to the subspecies now or in the foreseeable future. 
Food availability was also identified as a potential threat. However, 
food availability is naturally variable for most species and van 
Rossem's gull-billed terns are highly opportunistic and readily eat a 
wide variety of prey, making them less vulnerable to changes in 
available prey items than species with more specialized diets. As such, 
food availability is not likely to be a significant threat to van 
Rossem's gull-billed tern now or within the foreseeable future.
    Small population size is a threat that could leave van Rossem's 
gull-billed terns more vulnerable to stochastic environmental events 
and natural disasters, as well as genetic or demographic problems. The 
best available information suggests that the population size of this 
subspecies was likely always small, and it would appear that the range 
has recently expanded, suggesting that the overall population of the 
subspecies is not limited. Therefore, it is unlikely that small 
population size is a significant threat now or within the foreseeable 
future. Van Rossem's gull-billed terns move readily between and among 
populations between and potentially within years, and their wide range 
further ensures that small population size is currently not a 
significant threat, nor likely to become one in the foreseeable future.
    Sea-level rise resulting from climate change is generally predicted 
to impact coastal-nesting waterbirds like van Rossem's gull-billed 
tern; however, impacts are likely to vary from species to species and 
from nesting location to nesting location. While climate change could 
potentially affect van Rossem's gull-billed tern or its habitat, 
information that is currently available fails to provide evidence to 
support a premise that climate change is a significant threat to van 
Rossem's gull-billed tern. Climate change-related sea-level rise is not 
expected to be a significant threat on the U.S. nesting locations in 
the foreseeable future, and we have no evidence to suggest it will 
significantly threaten the subspecies' habitat in Mexico. Additionally, 
potential temperature increases associated with global climate change 
are not likely to significantly affect the subspecies throughout its 
range because van Rossem's gull-billed terns have behavioral 
adaptations to keep eggs within an acceptable temperature range for 
development even under very high environmental temperatures. Also, 
severe drought would likely not constitute a significant threat to the 
subspecies because most of its breeding range is coastal and marine 
food resources would likely be unaffected.
    Based on our review of the best scientific and commercial 
information available, we conclude that van Rossem's gull-billed tern 
is not threatened by other natural or manmade factors including nest 
site disturbance, intentional killing, contaminants, food availability, 
small population size, or climate change now or in the foreseeable 
future.

Finding

    As required by the Act, we considered the five factors in assessing 
whether van Rossem's gull-billed tern is threatened or endangered 
throughout all or a significant portion of its range. We examined the 
best scientific and commercial information available regarding the 
past, present, and future threats faced by the van Rossem's gull-billed 
tern. We reviewed the petition, information available in our files, and 
other available published and unpublished information. In considering 
what factors might constitute threats, we must look beyond the mere 
exposure of the species to the factor to determine whether the species 
responds to the factor in a way that causes actual impacts to the 
species. If there is exposure to a factor, but no response, or only a 
positive response, that factor is not a threat. If there is exposure 
and the species responds negatively, the factor may be a threat and we 
then attempt to determine how significant a threat it is. If the threat 
is significant, it may drive or contribute to the risk of extinction of 
the species such that the species warrants listing as threatened or 
endangered as those terms are defined by the Act. This does not 
necessarily require empirical proof of a threat. The combination of 
exposure and some corroborating evidence of how the species is likely 
impacted could suffice. The mere identification of factors that could 
impact a species negatively is not sufficient to compel a finding that 
listing is appropriate; we require evidence that these factors, alone 
or in combination, are operative threats that act on the species to the 
point that the species meets the definition of threatened or endangered 
under the Act.
    Although foraging and nesting habitat has been lost in the past 
within the range of van Rossem's gull-billed tern, the subspecies' 
flexibility in foraging and nesting reduces the impact such losses have 
on the subspecies. Unlike most tern species, the foraging habitat for 
the subspecies includes both upland habitat and wetland areas. 
Additionally, because the subspecies is a capable flyer, it can quickly 
and effectively move between areas in search of food. Nest sites for 
van Rossem's gull-billed terns are more restrictive; they nest on 
islands and other remote areas where the risk of predation, especially 
from terrestrial predators, is low. However, nest site fidelity is low, 
meaning van Rossem's gull-billed terns can and may move from one nest 
site to another, both

[[Page 58675]]

between years or within a given year, to renest after a predation or 
disturbance event. Thus, provided nesting habitat is available, they 
have no obvious behavioral limitations that prevent them from using it. 
As such, the subspecies is not highly susceptible to loss of nesting 
habitat and appears to be resilient to changes in habitat.
    Although there is the potential for eggs and young of ground-
nesting colonial waterbirds to be harvested in some areas in Mexico, 
the activity has never been reported to affect van Rossem's gull-billed 
terns. If it occurs now or in the foreseeable future, it is unlikely to 
occur at levels (temporally, geographically, or both) that pose a 
significant threat to the subspecies throughout its range or at any 
particular nesting location. Therefore, overutilization (Factor B) does 
not appear to be a significant threat to van Rossem's gull-billed tern 
at this time. Similarly, disease (including WNV) (Factor C) does not 
appear to be a significant threat at this time, and neither do 
contaminants (DDT/DDE and selenium) despite their presence in the 
environment where the subspecies nests and forages (Factor E).
    Nest predation (Factor C) and disturbance (Factor E) are a 
perennial problem for ground-nesting bird species. Van Rossem's gull-
billed terns nest on islands and other remote areas where the risk of 
predation and disturbance is generally low. Disturbance may be from 
naturally occurring species, humans, pets, or livestock. Should a major 
predation or disturbance event occur at a nest site, van Rossem's gull-
billed terns frequently relocate and renest. Thus, van Rossem's gull-
billed terns may still reproduce even when faced with nest predation or 
severe disturbance, thereby reducing the magnitude of these threats 
should they occur. Moreover, gull-billed terns are long-lived. Should a 
colony fail to reproduce in a given year, most of the adult birds will 
likely have other chances to reproduce. Thus, nest predation and 
disturbance do not significantly threaten the subspecies throughout its 
range now or within the foreseeable future.
    Managers of other species have targeted Van Rossem's gull-billed 
terns because they are predators. In the past, a few gull-billed terns 
were killed to protect California least tern and western snowy plover 
nest colonies (Factor E). However, no gull-billed terns have been 
killed recently for this purpose, and no lethal take permits have been 
granted for such activities. As such, predator control efforts (with 
van Rossem's gull-billed terns as the targets) are not a current 
threat. Although three van Rossem's gull-billed terns were killed to 
protect human health and safety (within the vicinity of active airport 
runways), these numbers of intentional loss are small and all such 
actions occurred within a population (the San Diego Bay population) 
that has grown continually since 1999. Additionally, unauthorized 
lethal control (shooting) of van Rossem's gull-billed terns over 
commercial shrimp aquaculture farms in Mexico has been observed. 
Although information on whether this activity is widespread is not 
readily available, our review of the available information does not 
indicate a significant level of impact on van Rossem's gull-billed 
terns.
    Van Rossem's gull-billed terns are generalist predators, 
opportunistically consuming a variety of available prey items. As a 
result, van Rossem's gull-billed terns may shift to other types of prey 
items should one become unavailable because of natural or human-
influenced changes. This is in contrast to most other tern species that 
depend on fish as their primary prey. It is unlikely that all potential 
prey items for van Rossem's gull-billed tern will be affected at the 
same time. However, should this occur, van Rossem's gull-billed terns 
are capable of flying to different locations to forage. If reduced 
abundance of prey was to occur in breeding areas, it would likely 
result in the loss of productivity for that year, but because van 
Rossem's gull-billed terns are long-lived, most individuals would be 
expected to survive to nest the following year. We have no information 
to suggest that van Rossem's gull-billed terns are facing food 
shortages. Therefore, food availability (Factor E) is not a significant 
threat to the subspecies.
    With an estimated minimum breeding population of approximately 
1,600 adults, the population size of van Rossem's gull-billed tern is 
one of the smallest of any tern taxon in North America. Compared to 
larger populations, small populations may be more likely to be affected 
disproportionately by demographic, genetic, or environmental factors. 
Although the population of van Rossem's gull-billed tern may be 
relatively small, its range appears to have recently expanded. This 
suggests that the population is not markedly affected by demographic or 
genetic bottlenecks. Additionally, inbreeding depression and genetic 
drift is less likely in a subspecies comprised of individuals that 
regularly move long distances and occur at different nesting locations 
from time to time, which van Rossem's gull-billed terns are known to 
do. Moreover, the wide range over which the subspecies breeds suggests 
that not all of the nesting areas would be simultaneously affected by 
catastrophic environmental events (droughts, floods, hurricanes). 
Therefore, although the small population size is a potential cause for 
concern, it does not appear that the threats associated with small 
population sizes (Factor E) are significantly affecting van Rossem's 
gull-billed tern and are not likely to in the foreseeable future.
    Sea-level rise resulting from climate change is generally predicted 
to impact coastal-nesting waterbirds like van Rossem's gull-billed tern 
(Factor E); however, the actual impacts are likely to vary from species 
to species and from nesting location to nesting location. While climate 
change could potentially affect van Rossem's gull-billed tern or its 
habitat, the limited amount of available information fails to provide 
evidence to support a premise that climate change is a significant 
threat to van Rossem's gull-billed tern.
    A species may be affected by more than one threat in combination. 
Within the preceding review of the five listing factors, we have 
identified multiple threats that may have interrelated impacts on the 
subspecies. For example, the productivity of van Rossem's gull-billed 
terns may be reduced because of the effects of predators (especially 
terrestrial predators) (Factor C) or nest-site disturbance (Factor E). 
Likewise, a physical change in nesting habitat (Factor A), such as an 
island becoming part of the mainland because of changes in water level, 
may allow for increased depredation or disturbance. Moreover, the 
subspecies' behavior of not nesting in areas where depredation or 
disturbance is likely may mean a nest site is ``abandoned'' before 
nesting is even attempted. Thus, the subspecies' productivity may be 
reduced because of these threats, either singularly or in combination. 
However, it is not necessarily easy to determine (nor is it necessarily 
determinable) which potential threat is the operational threat. As we 
discuss above, regardless of its source, we determine that such 
threats, either individually or in combination, are not likely to occur 
at a sufficient geographical or temporal scale to significantly affect 
the status of the species.
    Based on our review of the best available scientific and commercial 
information pertaining to the five factors, we find that the threats, 
alone or in combination, are not of sufficient imminence, intensity, or 
magnitude to indicate that van Rossem's gull-billed

[[Page 58676]]

tern is in danger of extinction (endangered), or likely to become 
endangered within the foreseeable future (threatened) throughout its 
range. Therefore, we find that listing van Rossem's gull-billed tern as 
an endangered or threatened species throughout its range is not 
warranted at this time.

Distinct Vertebrate Population Segments/Significant Portion of the 
Range

    After assessing whether the subspecies is endangered or threatened 
throughout its range, we next consider whether a distinct vertebrate 
population segment (DPS) exists and meets the definition of endangered 
or is likely to become endangered in the foreseeable future 
(threatened). We also consider whether the subspecies is endangered or 
threatened within a significant portion of its range. These assessments 
are discussed below.
Distinct Vertebrate Population Segment
    Under the joint DPS policy (61 FR 4722; February 7, 1996) of the 
Service and National Marine Fisheries Service, three elements are 
considered in the decision concerning the establishment and 
classification of a possible DPS. These are applied similarly for 
additions to or removal from the Federal List of Endangered and 
Threatened Wildlife. These elements include:
    (1) The discreteness of a population in relation to the remainder 
of the species to which it belongs;
    (2) The significance of the population segment to the species to 
which it belongs; and
    (3) The population segment's conservation status in relation to the 
Act's standards for listing, delisting, or reclassification (i.e., is 
the population segment endangered or threatened).
Discreteness
    Under the DPS policy, a population segment of a vertebrate taxon 
may be considered discrete if it satisfies either one of the following 
conditions:
    (1) It is markedly separated from other populations of the same 
taxon as a consequence of physical, physiological, ecological, or 
behavioral factors. Quantitative measures of genetic or morphological 
discontinuity may provide evidence of this separation.
    (2) It is delimited by international governmental boundaries within 
which differences in control of exploitation, management of habitat, 
conservation status, or regulatory mechanisms exist that are 
significant in light of section 4(a)(1)(D) of the Act.
    We reviewed available information to determine whether there are 
population segments of van Rossem's gull-billed tern that meet the 
first discreteness condition of our 1996 DPS policy. We found no 
evidence that population segments existed that were markedly separated 
from each other as a consequence of physical, physiological, 
ecological, or behavioral factors. We are not aware of measures of 
genetic or morphological discontinuity that provide evidence of marked 
separation. As noted previously, van Rossem's gull-billed terns are 
highly mobile. They are migratory and regularly move between breeding 
and wintering areas every year. In the subspecies' winter range, 
individuals can mix and mingle with other individuals. At the northern 
end of the subspecies' range, individuals have been observed to move 
between nesting locations between years (Molina and Garrett 2001, p. 
26; Patton 2001, p. 8; Molina 2004, p. 98), and the information we have 
suggests that such movements occur elsewhere within the subspecies' 
range. Even though a superficial examination of nesting locations 
(Figure 1) shows clusters of nesting locations somewhat geographically 
distant from other clusters, the biology of the subspecies suggests 
that interchange of individuals occurs between and among these 
clusters. In other words, an individual van Rossem's gull-billed tern 
that occurs within a given cluster of nesting locations during a given 
breeding season may occur within a different cluster of nesting 
locations the next year. As such, these geographically separated 
clusters are not biologically separate from each other. Therefore, no 
population of van Rossem's gull-billed tern meets the first 
discreteness condition of our 1996 DPS policy.
    We next evaluated whether any population segments meet the second 
discreteness condition of our 1996 DPS policy. Nest locations at San 
Diego Bay and Salton Sea can be delimited from all other nest locations 
in Mexico by an international governmental boundary (Figure 1). 
However, after evaluating available information, we have concluded that 
breeding populations at San Diego Bay and Salton Sea do not meet the 
second discreteness condition because differences in control of 
exploitation, management of habitat, conservation status, or regulatory 
mechanisms between the U.S. and Mexican populations are not significant 
in light of section 4(a)(1)(D) of the Act. Mexico and the United States 
are both signatories to the Migratory Bird Treaty Act, and two of the 
largest nesting populations of van Rossem's gull-billed terns in Mexico 
are located within biosphere reserves where development is limited by 
the LGEEPA (see Factor D).
    We determined, based on a review of the best available information, 
that there are no populations of van Rossem's gull-billed tern that 
meet the discreteness conditions of the 1996 DPS policy. The DPS policy 
is clear that significance is analyzed only when a population segment 
has been identified as discrete. Because we found no population 
segments that meet the discreteness element under the Service's DPS 
policy, we will not conduct an evaluation of significance under that 
policy. We conclude that no population segment qualifies as a listable 
DPS under the Act.
Significant Portion of the Range
    Having determined that the van Rossem's gull-billed tern is not 
endangered or threatened throughout its range, we must next consider 
whether there are any significant portions of the range where the van 
Rossem's gull-billed tern is in danger of extinction or is likely to 
become endangered in the foreseeable future.
    Decisions by the Ninth Circuit Court of Appeals in Defenders of 
Wildlife v. Norton, 258 F.3d 1136 (2001) and Tucson Herpetological 
Society v. Salazar, 566 F.3d 870 (2009) found that the Act requires the 
Service, in determining whether a species is endangered or threatened 
throughout a significant portion of its range, to consider whether lost 
historical range of a species (as opposed to its current range) 
constitutes a significant portion of the range of that species. While 
this is not our interpretation of the statute, we first address the 
lost historical range before addressing the current range.
Lost Historical Range
    The available literature provides little information on the 
historical breeding range of van Rossem's gull-billed tern. The only 
historical nesting location where nesting was confirmed was the Salton 
Sea (Pemberton 1927, p. 253). However, nesting was suspected at various 
locations along the west coast of mainland Mexico, possibly as far 
south as the state of Oaxaca (see Molina and Erwin 2006, pp. 273-274; 
see also the ``Range and Distribution'' section, above). Although 
nesting has been confirmed in modern times at certain nesting locations 
in western mainland Mexico--thereby validating the suspicions of 
historical observers at some, but not all, potential nesting 
locations--the historical breeding range of van Rossem's gull-billed 
tern everywhere except the Salton Sea is

[[Page 58677]]

ambiguous and will remain so forever. Thus, the historical breeding 
range of van Rossem's gull-billed tern may be characterized as follows: 
The Salton Sea and probably western mainland Mexico.
    With the exception of the Salton Sea nesting location (which was 
known historically, but could not have existed before the Salton Sea's 
creation in its modern form in 1907), the confirmation of all other van 
Rossem's gull-billed tern nesting locations occurred in modern times 
(1987 and later). Available information on modern nesting locations is 
summarized in Table 1, with additional discussion in the ``Range and 
Distribution'' section, above. As noted in that section, the current 
southernmost confirmed nesting location is Laguna Potos[iacute], 
Guerrero, but nesting farther south in Mexico continues to be a 
possibility. As such, despite increased certainty of the subspecies' 
current breeding range in western Mexico compared to its historical 
range, the southern limit of that range remains ambiguous. Thus, the 
current breeding range of the subspecies may be characterized as 
follows: The Salton Sea and south through the greater Colorado River 
delta region, San Diego Bay, Laguna Ojo de Liebre (Baja California 
Sur), and western mainland Mexico at least as far south as Laguna 
Potos[iacute] (Guerrero) but possibly farther south.
    Although we acknowledge that there is ambiguity in the historical 
and modern breeding ranges, the ambiguities are from essentially the 
same geographical area, the southern Pacific coast of Mexico (and 
possibly the Pacific coast of Central America). The ambiguity in the 
modern breeding range is essentially a perpetuation of the ambiguity in 
the historical breeding range. Thus, the best available information 
indicates that the current breeding range of van Rossem's gull-billed 
tern--with the modern colonizations of San Diego Bay and Laguna Ojo de 
Liebre--is larger than the subspecies' historical breeding range. Thus, 
we conclude that no portions of the subspecies' breeding range have 
been lost.
    Little information is available on the historical winter range of 
van Rossem's gull-billed tern. Even today, the current winter range is 
not well defined. The lack of historical and modern information, 
especially for the southern portion of the subspecies' range, results 
in historical and current winter ranges that are ambiguous (see the 
``Range and Distribution'' section for details), much in the way the 
breeding ranges are ambiguous. After reviewing the available 
information, the historical and current winter ranges of van Rossem's 
gull-billed tern can be characterized as follows: Coastal western 
Mexico and possibly western Central America. We are not aware of any 
differences between the subspecies' current winter range compared to 
its historical winter range. Thus, we conclude that no portions of the 
subspecies' winter range have been lost.
    Information on the areas over which van Rossem's gull-billed terns 
migrate is also limited. That area has likely had a corresponding 
increase associated with the modern colonization of nesting sites along 
the Pacific coast of the Baja California Peninsula, Mexico, and extreme 
southwestern United States. Thus, we conclude that no portions of the 
subspecies' range used for migration have been lost. Therefore, there 
is no lost historical range of van Rossem's gull-billed tern that could 
constitute a significant portion of the range of the subspecies.
Current Range
    The Act defines ``endangered species'' as any species which is ``in 
danger of extinction throughout all or a significant portion of its 
range,'' and ``threatened species'' as any species which is ``likely to 
become an endangered species within the foreseeable future throughout 
all or a significant portion of its range.'' The definition of 
``species'' is also relevant to this discussion. The Act defines 
``species'' as follows: ``The term `species' includes any subspecies of 
fish or wildlife or plants, and any distinct population segment [DPS] 
of any species of vertebrate fish or wildlife which interbreeds when 
mature.'' The phrase ``significant portion of its range'' (SPR) is not 
defined by the statute, and we have never addressed in our regulations: 
(1) The consequences of a determination that a species is either 
endangered or likely to become so throughout a significant portion of 
its range, but not throughout all of its range; or (2) what qualifies a 
portion of a range as ``significant.''
    Two recent district court decisions have addressed whether the SPR 
language allows the Service to list or protect less than all members of 
a defined ``species'': Defenders of Wildlife v. Salazar, 729 F. Supp. 
2d 1207 (D. Mont. 2010), concerning the Service's delisting of the 
Northern Rocky Mountain gray wolf (74 FR 15123, Apr. 12, 2009); and 
WildEarth Guardians v. Salazar, 2010 U.S. Dist. LEXIS 105253 (D. Ariz. 
Sept. 30, 2010), concerning the Service's 2008 finding on a petition to 
list the Gunnison's prairie dog (73 FR 6660, Feb. 5, 2008). The Service 
had asserted in both of these determinations that it had authority, in 
effect, to protect only some members of a ``species,'' as defined by 
the Act (i.e., species, subspecies, or DPS), under the Act. Both courts 
ruled that the determinations were arbitrary and capricious on the 
grounds that this approach violated the plain and unambiguous language 
of the Act. The courts concluded that reading the SPR language to allow 
protecting only a portion of a species' range is inconsistent with the 
Act's definition of ``species.'' The courts concluded that once a 
determination is made that a species (i.e., species, subspecies, or 
DPS) meets the definition of ``endangered species'' or ``threatened 
species,'' it must be placed on the list in its entirety and the Act's 
protections applied consistently to all members of that species 
(subject to modification of protections through special rules under 
sections 4(d) and 10(j) of the Act).
    Consistent with that interpretation, and for the purposes of this 
finding, we interpret the phrase ``significant portion of its range'' 
in the Act's definitions of ``endangered species'' and ``threatened 
species'' to provide an independent basis for listing; thus there are 
two situations (or factual bases) under which a species would qualify 
for listing: A species may be endangered or threatened throughout all 
of its range; or a species may be endangered or threatened in only a 
significant portion of its range. If a species is in danger of 
extinction throughout an SPR, it, the species, is an ``endangered 
species.'' The same analysis applies to ``threatened species.'' Based 
on this interpretation and supported by existing case law, the 
consequence of finding that a species is endangered or threatened in 
only a significant portion of its range is that the entire species 
shall be listed as endangered or threatened, respectively, and the 
Act's protections shall be applied across the species' entire range.
    We conclude, for the purposes of this finding, that interpreting 
the SPR phrase as providing an independent basis for listing is the 
best interpretation of the Act because it is consistent with the 
purposes and the plain meaning of the key definitions of the Act; it 
does not conflict with established past agency practice (i.e., prior to 
the 2007 Solicitor's Opinion), as no consistent, long-term agency 
practice has been established; and it is consistent with the judicial 
opinions that have most closely examined this issue. Having concluded 
that the phrase ``significant portion of its range'' provides an 
independent basis for listing and protecting the entire species, we 
next turn to the meaning of ``significant'' to determine the threshold

[[Page 58678]]

for when such an independent basis for listing exists.
    Although there are potentially many ways to determine whether a 
portion of a species' range is ``significant,'' we conclude, for the 
purposes of this finding, that the significance of the portion of the 
range should be determined based on its biological contribution to the 
conservation of the species. For this reason, we describe the threshold 
for ``significant'' in terms of an increase in the risk of extinction 
for the species. We conclude that a biologically based definition of 
``significant'' best conforms to the purposes of the Act, is consistent 
with judicial interpretations, and best ensures species' conservation. 
Thus, for the purposes of this finding, and as explained further below, 
a portion of the range of a species is ``significant'' if its 
contribution to the viability of the species is so important that 
without that portion, the species would be in danger of extinction.
    We evaluate biological significance based on the principles of 
conservation biology using the concepts of redundancy, resiliency, and 
representation. Resiliency describes the characteristics of a species 
and its habitat that allow it to recover from periodic disturbance. 
Redundancy (having multiple populations distributed across the 
landscape) may be needed to provide a margin of safety for the species 
to withstand catastrophic events. Representation (the range of 
variation found in a species) ensures that the species' adaptive 
capabilities are conserved. Redundancy, resiliency, and representation 
are not independent of each other, and some characteristic of a species 
or area may contribute to all three. For example, distribution across a 
wide variety of habitat types is an indicator of representation, but it 
may also indicate a broad geographic distribution contributing to 
redundancy (decreasing the chance that any one event affects the entire 
species), and the likelihood that some habitat types are less 
susceptible to certain threats, contributing to resiliency (the ability 
of the species to recover from disturbance). None of these concepts is 
intended to be mutually exclusive, and a portion of a species' range 
may be determined to be ``significant'' due to its contributions under 
any one or more of these concepts.
    For the purposes of this finding, we determine if a portion's 
biological contribution is so important that the portion qualifies as 
``significant'' by asking whether without that portion, the 
representation, redundancy, or resiliency of the species would be so 
impaired that the species would have an increased vulnerability to 
threats to the point that the overall species would be in danger of 
extinction (i.e., would be ``endangered''). Conversely, we would not 
consider the portion of the range at issue to be ``significant'' if 
there is sufficient resiliency, redundancy, and representation 
elsewhere in the species' range that the species would not be in danger 
of extinction throughout its range if the population in that portion of 
the range in question became extirpated (extinct locally).
    We recognize that this definition of ``significant'' (a portion of 
the range of a species is ``significant'' if its contribution to the 
viability of the species is so important that without that portion, the 
species would be in danger of extinction) establishes a threshold that 
is relatively high. On the one hand, given that the consequences of 
finding a species to be endangered or threatened in an SPR would be 
listing the species throughout its entire range, it is important to use 
a threshold for ``significant'' that is robust. It would not be 
meaningful or appropriate to establish a very low threshold whereby a 
portion of the range can be considered ``significant'' even if only a 
negligible increase in extinction risk would result from its loss. 
Because nearly any portion of a species' range can be said to 
contribute some increment to a species' viability, use of such a low 
threshold would require us to impose restrictions and expend 
conservation resources disproportionately to conservation benefit: 
listing would be rangewide, even if only a portion of the range of 
minor conservation importance to the species is imperiled. On the other 
hand, it would be inappropriate to establish a threshold for 
``significant'' that is too high. This would be the case if the 
standard were, for example, that a portion of the range can be 
considered ``significant'' only if threats in that portion result in 
the entire species' being currently endangered or threatened. Such a 
high bar would not give the SPR phrase independent meaning, as the 
Ninth Circuit held in Defenders of Wildlife v. Norton, 258 F.3d 1136 
(9th Cir. 2001).
    The definition of ``significant'' used in this finding carefully 
balances these concerns. By setting a relatively high threshold, we 
minimize the degree to which restrictions will be imposed or resources 
expended that do not contribute substantially to species conservation. 
But we have not set the threshold so high that the phrase ``in a 
significant portion of its range'' loses independent meaning. 
Specifically, we have not set the threshold as high as it was under the 
interpretation presented by the Service in the Defenders litigation. 
Under that interpretation, the portion of the range would have to be so 
important that current imperilment there would mean that the species 
would be currently imperiled everywhere. Under the definition of 
``significant'' used in this finding, the portion of the range need not 
rise to such an exceptionally high level of biological significance. 
(We recognize that if the species is imperiled in a portion that rises 
to that level of biological significance, then we should conclude that 
the species is in fact imperiled throughout all of its range, and that 
we would not need to rely on the SPR language for such a listing.) 
Rather, under this interpretation we ask whether the species would be 
endangered everywhere without that portion, i.e., if that portion were 
completely extirpated. In other words, the portion of the range need 
not be so important that even the species being in danger of extinction 
in that portion would be sufficient to cause the species in the 
remainder of the range to be endangered; rather, the complete 
extirpation (in a hypothetical future) of the species in that portion 
would be required to cause the species in the remainder of the range to 
be endangered.
    The range of a species can theoretically be divided into portions 
in an infinite number of ways. However, there is no purpose to 
analyzing portions of the range that have no reasonable potential to be 
significant or to analyzing portions of the range in which there is no 
reasonable potential for the species to be endangered or threatened. To 
identify only those portions that warrant further consideration, we 
determine whether there is substantial information indicating that: (1) 
The portions may be ``significant,'' and (2) the species may be in 
danger of extinction there or likely to become so within the 
foreseeable future. Depending on the biology of the species, its range, 
and the threats it faces, it might be more efficient for us to address 
the significance question first or the status question first. Thus, if 
we determine that a portion of the range is not ``significant,'' we do 
not need to determine whether the species is endangered or threatened 
there; if we determine that the species is not endangered or threatened 
in a portion of its range, we do not need to determine if that portion 
is ``significant.'' In practice, a key part of the determination that a 
species is in danger of extinction in a significant portion of its 
range is

[[Page 58679]]

whether the threats are geographically concentrated in some way. If the 
threats to the species are essentially uniform throughout its range, no 
portion is likely to warrant further consideration. Moreover, if any 
concentration of threats to the species occurs only in portions of the 
species' range that clearly would not meet the biologically based 
definition of ``significant,'' such portions will not warrant further 
consideration.
    After reviewing the potential threats throughout the range of van 
Rossem's gull-billed tern, we determine that there may be two portions 
of the tern's breeding range that could be considered to have 
concentrated threats for the subspecies there. Below, we outline the 
elevated threats found at two nesting locations, the Salton Sea in 
California and the islands in the impoundments associated with Campo 
Geot[eacute]rmico Cerro Prieto (Cerro Prieto geothermal generation 
facility) in northeast Baja California (Table 1, Figure 1). We then 
assess whether these portions of the subspecies' breeding range may 
meet the biologically based definition of ``significant,'' that is, 
whether the contributions of these portions of the gull-billed tern's 
range to the viability of the subspecies is so important that without 
those portions, the species would be in danger of extinction.
    The decreasing water levels at the nesting location at Salton Sea 
and changing water storage practices at the nesting location at Cerro 
Prieto have the potential to be considered as concentrations of threats 
at each of these nesting locations (see Summary of Information 
Pertaining to the Five Factors). The observed and anticipated reduction 
in water levels at these locations may lead to an increase in nest 
predation (Factor C) at either site. Increased nest predation would 
likely result in reduced reproductive output. Moreover, the subspecies' 
behavior of selecting islands and other areas where terrestrial nest 
predators are less likely to occur makes the relative lack of predators 
part of what constitutes nesting habitat for this subspecies. Thus, 
observed and anticipated changes in water levels may also lead to a 
loss of nesting habitat at the respective locations (Factor A).
    In general, for taxa that are sessile (anchored) or of limited 
mobility, loss of habitat would typically translate into some 
concurrent loss of individuals, which in turn would translate into some 
concomitant effect on the overall population. However, individual adult 
van Rossem's gull-billed terns are highly mobile; they can and do move, 
both in terms of their seasonal migratory movements and in terms of 
their ability to move between nesting locations from year to year and 
within years. For example, if van Rossem's gull-billed terns returning 
from their wintering areas found that a particular nesting location no 
longer provided nesting habitat, the available information suggests 
that the birds can and would move to a different nesting location. 
Thus, habitat loss at either of these nesting locations would not 
necessarily result in a direct reduction in the subspecies' overall 
population. However, we expect that moving to a different nesting 
location would not be without consequences. Instead, we expect that the 
relocated birds would concentrate in other existing nesting locations 
(in potentially lower quality nest sites within existing nesting 
locations) or that they would occupy new, potentially less-suitable 
(lower quality) nesting locations. Consequently, the effects of the 
loss of nesting habitat would likely result in reduced reproductive 
output by the subspecies.
    Because the van Rossem's gull-billed tern faces elevated threats at 
the Salton Sea and Cerro Prieto nesting locations, we next assess 
whether these portions of the subspecies' breeding range may meet the 
biologically based definition of ``significant.'' For both areas, we 
evaluate whether the portion's biological contribution is so important 
that the portion qualifies as ``significant'' by asking whether without 
that portion, the representation, redundancy, or resiliency of the 
species' would be so impaired that the species would have an increased 
vulnerability to threats to the point that the overall species would be 
in danger of extinction.
    Although each nesting location has features that make it unique, we 
have no evidence, whether based on the locations' geography or the 
subspecies' biology, that suggests these nesting locations are markedly 
different from any other nesting location. For example, the nesting 
habitat is essentially the same at all nesting locations. As with 
nesting habitat, the subspecies' foraging habitat is similar throughout 
its range, whether during the breeding season, winter, or migration. 
Although coastal nesting locations are more common than the inland 
nesting locations that Salton Sea and Cerro Prieto represent, van 
Rossem's gull-billed terns essentially nest in the same types of areas 
inland as they do in coastal nesting locations. Gull-billed terns 
(subspecies unknown) have also been observed nesting at other inland 
locations in Mexico (G[oacute]mez de Silva 2005, p. 501; Molina and 
Erwin 2006, p. 274) (see the ``Range and Distribution'' section, 
above).
    As mobile birds, individual van Rossem's gull-billed terns are not 
tied to any particular nesting location, and often move between nesting 
locations. Van Rossem's gull-billed terns that nest at either the 
Salton Sea or Cerro Prieto are not permanent occupants of either 
location. Van Rossem's gull-billed terns leave each of these areas to 
winter farther south. As stated under ``Biology'' in the Species 
Information section, van Rossem's gull-billed terns appear to be 
opportunistic and adaptable nesters, displaying low nest-site fidelity, 
and even moving to new sites and renesting within the same year. Groups 
of van Rossem's gull-billed terns have displayed such renesting 
behavior at the Salton Sea (Molina 2009b, pp. 6-7) and at Bah[iacute]a 
Santa Mar[iacute]a (Palacios and Mellink 2007, p. 218). Van Rossem's 
gull-billed terns will readily take advantage of new nest sites as well 
as sites that are not available every year (for example, Molina 2005, 
p. 4; Molina 2009b, p. 2). If the Salton Sea and Cerro Prieto could no 
longer support nesting, other existing and potential nesting locations 
are distributed along a 2,250-km (1,400-mi) stretch of the subspecies' 
breeding range from southern California to Guerrero, Mexico (see Figure 
1). There are currently nine nesting locations along the coast with 
multiple nest sites where breeding colonies have been documented. There 
is sufficient representation and redundancy of nesting habitat in the 
subspecies' breeding range such that van Rossem's gull-billed tern 
would not be in danger of extinction if either or both of the Salton 
Sea and Cerro Prieto nesting locations were completely lost.
    Elimination of the Salton Sea and Cerro Prieto nesting locations 
would not result in the elimination of the individual van Rossem's 
gull-billed terns that would have otherwise nested at those locations. 
The loss of both or either of the Salton Sea or Cerro Prieto portions 
of the subspecies' range would not directly result in a reduction in 
the subspecies' overall population, but there may be a temporary 
reduction in the local populations' reproductive output compared to 
what it would have been. This potential reduction of reproductive 
output is not expected to reduce the subspecies' range of variation or 
adaptive capabilities to such a level that they would be in danger of 
extinction. Without these two nesting locations, we expect that the 
resiliency of van Rossem's gull-billed tern would not be appreciably 
impacted; the subspecies would continue to be able to recover from 
periodic disturbance and

[[Page 58680]]

withstand catastrophic events in other parts of its range.
    In summary, although there are elevated threats related to 
potential changes in water level at Cerro Prieto and Salton Sea, these 
portions of the van Rossem's gull-billed tern's range are not 
significant portions of its range. Even if these nesting colonies were 
abandoned at some time in the future, it is likely that van Rossem's 
gull-billed terns would move and nest elsewhere, as they are not tied 
to any particular nesting location. As noted above, there is little 
that biologically distinguishes either Cerro Prieto or the Salton Sea 
from other nesting locations for van Rossem's gull-billed tern. They 
each happen to be inland, which undoubtedly contributes to the shared 
threat of changes in water levels, but the nesting and foraging areas 
at each of these sites do not differ notably from those in the 
subspecies' entire range. Existing and potential nesting locations are 
distributed along a 2,250-km (1,400-mi) stretch of the subspecies' 
breeding range from southern California to Guerrero, Mexico. Neither 
Cerro Prieto nor the Salton Sea, nor even the two nesting locations 
combined, is a ``significant'' portion of the species' range because 
their contribution to the viability of the subspecies is not so 
important that the subspecies would be in danger of extinction without 
those portions.
    We find that van Rossem's gull-billed tern is not in danger of 
extinction now, nor is it likely to become endangered within the 
foreseeable future throughout all or a significant portion of its 
range. Therefore, listing van Rossem's gull-billed tern as endangered 
or threatened under the Act is not warranted at this time.
    We request that you submit any new information concerning the 
status of, or threats to, van Rossem's gull-billed tern to our Carlsbad 
Fish and Wildlife Office (see ADDRESSES section) whenever it becomes 
available. New information will help us monitor van Rossem's gull-
billed tern and encourage its conservation. If an emergency situation 
develops for the van Rossem's gull-billed tern or any other species, we 
will act to provide immediate protection.

References Cited

    A complete list of references cited is available on the Internet at 
http://www.regulations.gov and upon request from the Carlsbad Fish and 
Wildlife Office (see ADDRESSES section).

Authors

    The primary authors of this notice are staff members of the 
Carlsbad Fish and Wildlife Office.

    Authority:  The authority for this section is section 4 of the 
Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: September 9, 2011.
Daniel M. Ashe,
Director, Fish and Wildlife Service.
[FR Doc. 2011-24048 Filed 9-20-11; 8:45 am]
BILLING CODE 4310-55-P