[Federal Register Volume 60, Number 58 (Monday, March 27, 1995)]
[Rules and Regulations]
[Pages 15693-15699]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-7549]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
Endangered and Threatened Wildlife and Plants; Notice of
Determination To Retain the Threatened Status for the Coastal
California Gnatcatcher Under the Endangered Species Act
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of determination.
-----------------------------------------------------------------------
SUMMARY: The Fish and Wildlife Service (Service), announces a
determination affirming its earlier conclusion (March 30, 1993; 58 FR
16742) that the coastal California gnatcatcher (Polioptila californica
californica), a small, insectivorous songbird, is a distinct subspecies
and, thus, meets the definition of a ``species'' pursuant to the
Endangered Species Act of 1973, as amended (Act). In addition, the
Service affirms its earlier conclusion (58 FR 16742) that the southern
limit of this subspecies extends to about 30 deg. north latitude near
the vicinity of El Rosario, Baja California, Mexico. Based on these
determinations, the Service concludes that its March 30, 1993, decision
that the coastal California gnatcatcher is a threatened species was
correct. Federal protection for the coastal California gnatcatcher is
thus continued.
EFFECTIVE DATE: March 23, 1995.
ADDRESSES: The complete administrative records and files for this
determination and all related rule promulgations and notices are
available for inspection, by appointment, during normal business hours
at the Fish and Wildlife Service Carlsbad Field Office, 2730 Loker
Avenue West, Carlsbad, California 92008.
FOR FURTHER INFORMATION CONTACT: Mr. Gail C. Kobetich, Field
Supervisor, at the above address (telephone 619/431-9440).
SUPPLEMENTARY INFORMATION:
Background
The coastal California gnatcatcher (Polioptila californica
californica), a subspecies of the California gnatcatcher, is a small,
long-tailed member of the thrush family Muscicapidae. The subspecies is
restricted to California and Baja California, Mexico, and is an
obligate resident of coastal sage scrub, which is one of the most
depleted habitat types in the United States (58 FR 16742). The plumage
color of the species is dark blue-gray above and grayish-white below.
The tail is mostly black above and below. This subspecies is
distinguished from the other subspecies by its darker body plumage,
less extensive white on tail feathers (rectrices 5 and 6), and longer
tail (Atwood 1991). The male has a distinctive black cap that is absent
during the winter. Both sexes have a distinctive white eye-ring.
Vocalizations of this species include a call consisting of a rising and
falling series of three kitten-like mew notes (National Geographic
Society 1983).
The California gnatcatcher was originally described as a distinct
species (Polioptila californica) by Brewster (1881) based on specimens
collected by Stephens in 1878. Later taxonomic treatments (e.g., Coues
1903 and Chapman 1903) reflected Brewster's (1881) conclusions.
Grinnell (1926), however, later concluded that the species was a form
of the black-tailed gnatcatcher (Polioptila melanura), which inhabits
the Sonoran and Chihuahuan Deserts of the southwestern United States
and northwestern Mexico. Subsequent scientific publications (American
Ornithologists' Union 1931, Grinnell and Miller 1944, Friedmann 1957,
American Ornithologists' Union 1957) adhered to the species limits as
defined by Grinnell (1926). Three subspecies of the black-tailed
gnatcatcher were recognized for southwestern California and western
Baja California, Mexico: P. m. californica (ranging from Los Angeles
County, California (formerly northward to Ventura County), south to
about 30 deg. north latitude in Baja California, Mexico), P. m.
pontilis (resident in central Baja California), and P. m. margaritae
(ranging from about 27 deg. north latitude south to the Cape region of
Baja California) (American Ornithologists' Union 1957).
Based on identified differences in ecology and behavior that were
elucidated as a result of specimen study and statistical analysis,
Atwood (1988) proposed that Polioptila californica was specifically
distinct from P. melanura. This finding was subsequently formally
adopted by the American Ornithologists' Union Committee on
Classification and Nomenclature (American Ornithologists' Union 1989),
thus affirming Brewster's (1881) original taxonomic placement with
respect to species. The American Ornithologists' Union 1989 publication
did not address subspecies other than to refer the reader to the
American Ornithologists' Union 1957 checklist of North American birds.
The coastal California gnatcatcher, Polioptila californica
(=melanura) californica, has been recognized as a distinct race or
subspecies since Grinnell's (1926) publication (e.g., American
Ornithologists' Union 1931, Grinnell and Miller 1944, Friedmann 1957,
American Ornithologists' Union 1957, Garrett and Dunn 1981, Unitt 1984,
Phillips 1991, Atwood 1991). As indicated above, this subspecies occurs
from Los Angeles County (and, formerly, Ventura County) south to about
30 deg. north latitude in Baja California, Mexico. Although Atwood
(1988) proposed merging P. californica californica with a more
southerly subspecies of P. californica, he later (1991) retracted this
conclusion.
On March 30, 1993, the Service published a final rule determining
the coastal California gnatcatcher (Polioptila californica californica)
to be a threatened species (58 FR 16741). In making this determination,
the Service relied, in part, on taxonomic studies conducted by Dr.
Jonathan Atwood of the Manomet Bird Observatory. As is standard
practice in the scientific community, the Service did not request, nor
was it offered, the data collected and utilized by Atwood in reaching
his conclusions. Instead, the Service cited the conclusions presented
by Atwood in a peer reviewed, published scientific article pertaining
to the subspecific taxonomy of the California gnatcatcher (Atwood
1991).
The Endangered Species Committee of the Building Industry
Association of Southern California and other plaintiffs subsequently
filed a suit challenging the listing on several grounds. In a
Memorandum Opinion and Order filed in the United States District Court
for the District of Columbia on May 2, 1994, the Court vacated the
listing determination, holding that the [[Page 15694]] Secretary of
Interior (Secretary) should have made available the underlying data
that formed the basis of the Atwood (1988) report in light of the
controversy surrounding inconsistent conclusions reached by Atwood in
his 1988 and 1991 studies.
Following the Court's decision, Atwood released his data to the
Service. These data were, in turn, made available to the public for
review and comment on June 2, 1994 (59 FR 28508). By order of June 16,
1994, the Court reinstated threatened status for the coastal California
gnatcatcher pending a determination by the Secretary whether the
listing should be revised or revoked in light of his review of the
subject data and public comments received during public comment
periods. This notice constitutes the Service's determination in
response to the Court's June 16, 1994, order.
Summary of Comments and Recommendations
A proposed rule to list the gnatcatcher as endangered was published
on September 17, 1991 (56 FR 47053). Public comments were solicited and
two public hearings were held on the proposed rule. Notification of the
hearings was published in the Federal Register on February 7, 1992 (57
FR 4747). A legal notice announcing the hearings and inviting general
public comment on the proposal was also published on February 7, 1992
in the Los Angeles Daily News, Los Angeles Times, Riverside Press-
Enterprise, and the San Diego Union-Tribune. Public hearings were
conducted in Anaheim, California, on February 25, 1992, and in San
Diego, California, on February 27, 1992. A notice of extension and
reopening of the comment period for 30 days to obtain additional
information on gnatcatcher taxonomy was published on September 22, 1992
(57 FR 43688). On February 11, 1993, the Service published a notice
announcing the reopening of the public comment period on the proposed
rule for 20 days and the availability of a report prepared by Service
taxonomists on the taxonomic validity of P. c. californica (58 FR
8032). On March 30, 1993, the Service published a final rule
determining the coastal California gnatcatcher to be a threatened
species (58 FR 16741). That same day, a proposed special rule pursuant
to section 4(d) of the Act was published (58 FR 16758). The final
special rule was published on December 10, 1993 (58 FR 65088).
Following the Court's Order of May 2, 1994, and receipt of Atwood's
data, the Service announced the availability of these data and the
opening of a public comment period on June 2, 1994 (58 FR 28508).
Atwood's data were sent to 15 parties upon request. With the approval
of the Court, the public comment period was extended to December 1,
1994 (59 FR 53628), to allow the public additional time to receive and
then comment upon the raw data and methodology utilized by Atwood.
During this 6-month public comment period, Dr. William Link and Mr.
Grey Pendleton of the National Biological Service, Department of the
Interior (Department), conducted a new and independent analysis of
Atwood's data (Link and Pendleton in litt. 1994). To assure that the
Service utilizes the best scientific information available in the
implementing the Act, it is policy (59 FR 34270) to seek independent
review of the scientific basis for listing and recovery actions.
Consistent with this policy, the Service solicited comments on the
National Biological Service document and all other public comments
received by December 1, 1994, from the general public, including
scientists with an expertise in avian taxonomy. A new 30-day public
comment period (59 FR 66509) was opened on December 27, 1994, to allow
the public to review and comment on these documents. This final comment
period closed on January 26, 1995.
A total of 31 comments pertaining to either (1) Atwood's data,
methodology, or results, or (2) the taxonomy of the gnatcatcher was
received during the final two comment periods. This total includes 21
comments received prior to December 1, 1994, and an additional 10
comments received during the final comment period. Included among the
comments were three new, independent analyses of Atwood's data. After a
review and consideration of all such comments, five relevant issues
have been identified and are discussed below. The five issues encompass
all substantive comments pertaining specifically to Atwood's data,
analyses, and conclusions regarding the taxonomy and geographic range
of the coastal California gnatcatcher.
Issue 1: Several commenters noted that Atwood's apparent discarding
of raw data precludes an appropriate analysis of his conclusions. One
commenter in particular was disturbed that ``Atwood no longer has the
raw data used in his original analyses.'' Another commenter noted that
Atwood admitted to discarding computer programs used in the analysis of
the data subsequently analyzed and reported in his 1991 publication.
Some stated that differences existed between the data sets used in
Atwood (1988), Atwood (1991) and that provided to the Service and the
public (Atwood in litt. 1994a).
Service Response: Atwood (in litt. 1994b) has stated that the
measurements provided to the general public following the May 2, 1994,
Court Order ``represent the total and unmodified data set that formed
the basis for my 1988 and 1991 publications on gnatcatcher
morphology.'' Atwood (in litt. 1994b) also indicated that only one
difference existed between the computer file data set transmitted to
the public and the data on the original paper forms that he discarded
after entering the data into a computer file, the sex of a single
specimen from sample area SI29 was corrected. Atwood (in litt. 1994b)
further indicated that he verified (in 1985) the data on the computer
by comparing it with the hand-written information on the paper forms.
The Service concludes that there is no reason to doubt the veracity of
Atwood in this regard.
Because data on paper forms cannot readily be subjected to
statistical analysis, the data transferred to a computer or computer
disk are, in essence, the raw data at issue. The Service, therefore,
rejects the contention that Atwood discarded his raw data, thereby
precluding reanalysis of the data.
After providing his data, Atwood realized that discrepancies in
sample size existed between data reported in his dissertation, his
monograph (Atwood 1988), his subspecies paper (Atwood 1991), and data
provided to the Service. He noted that for site SI29 there was a
discrepancy with respect to one female and one male specimen and
concluded that he had corrected the sex for one individual. His
dissertation revealed 14 specimens for sites PP28 and MA30, whereas the
Service data includes 13 specimens for site PP28 and 15 for site MA30.
Atwood believes that this discrepancy was the result of correctly
placing one specimen in site MA30 rather than PP28. These two
corrections resulted in apparent discrepancies. Atwood was unable to
explain an additional discrepancy, in his dissertation he reported 19
female specimens for site SD24, whereas the data provided to the
Service indicates 20 female specimens for site SD24; Atwood suggested
that a typographical error had occurred.
Atwood discovered numerous discrepancies between the sample sizes
for his monograph (Atwood 1988) and the data given to the Service
(amounting to 15 more male specimens and 7 fewer female specimens
reported in the Service data set). Atwood could not conclusively
explain these [[Page 15695]] discrepancies, but suspected that they
were associated with the differing lengths of data set lines that may
have caused the SAS program to skip lines or combine lines of data. He
suggested that this problem may also have affected his analyses of the
data presented in the 1988 monograph. He indicated that because of
these potential problems, he felt that it is inappropriate to rely upon
the 1988 monograph with respect to subspecific conclusions, although
the conclusions with respect to species were unaffected, and are valid.
However, programming errors would not have affected the original data
set.
Atwood (in litt. 1994a,b) has acknowledged that one of the 213
samples in the data set provided to the public was not used in his 1991
study or in his previous, unpublished status review of the gnatcatcher.
Atwood (in litt. 1994b) believes that the excluded specimen was that
designated YP2717, an aberrant specimen (possibly a black-tailed
gnatcatcher or interspecies hybrid) collected in 1885. In Atwood's
subsequent reanalysis of the original data set, specimen YP2717 was
excluded from the data set because it differed from its sample area
mean by more than 3 standard deviations (Atwood in litt. 1994b).
The sample size discrepancies for all reports, except the 1988
monograph, are very minor, and would not have affected the overall
conclusions of the authors. Atwood (1994b) has characterized the
analysis of his 1988 monograph as being ``seriously flawed'' with
respect to data processing. The sample size discrepancies between
Atwood's other reports, and the 1988 monograph are likely due to these
data processing problems, and not the result of changes made to the
data set. The Service, therefore, concludes that the data set provided
by Atwood to the Service adequately duplicates the data originally
written on paper forms.
Issue 2: One commenter noted that two of Atwood's publications
(1988 and 1991) were contradictory in that they proposed different
geographic ranges for the taxon of California gnatcatchers occurring in
the United States. This same commenter suggested that Atwood's (1991)
retraction of his original (1988) conclusions pertaining to the
subspecies taxonomy of the California gnatcatcher was prompted by his
desire to affect the listing of the species.
Service Response: While the record indicates that Atwood believes
that the listing of the coastal California gnatcatcher is warranted,
the record also indicates that Dr. Atwood's revised conclusion about
the subspecific geographic limits of Polioptila californica californica
resulted from his 1991 reanalysis of the data cited in his 1988
monograph. The (1988) monograph had received peer review critical of
its findings.
The Service receives dozens of petitions to list or delist species
each year. The Act requires the Service to conduct an independent
review of each of these petitions, and to make final decisions on the
basis of the best scientific data available. The motives of the
petitioners, as with commenters, are not relevant to the Service's
decisions on these issues.
Issue 3: Several commenters alleged fundamental flaws in the data
used by Atwood (1991) in generating his conclusions. In particular,
commenters suggested or concluded that the data appeared to be
incomplete, or non-random (i.e., ``censored''). Several commenters were
concerned that the variables were ``confounded'' (i.e., the effects of
two or more factors on a response variable could not be separated) due
to the age or condition of certain specimens. These commenters
indicated that for the northern sites nearly all specimens were
collected prior to 1940, and none of the specimens from the remaining
sites were collected prior to 1920. One commenter noted that a
potential exists for serious bias in the data due to specimen
``foxing'' (i.e., browning with age). Another commenter noted, citing
relevant published scientific literature, that body size and plumage
brilliance and iridescence can reflect variation in specimen condition.
Some of these commenters suggested that differences in characters among
sites may be the result of the age of the collection, and not the site
from which they were collected.
Service Response: On behalf of the Service, the National Biological
Service independently conducted a new analysis of Atwood's data (Link
and Pendleton in litt. 1994). Three additional independent analyses of
the data were also submitted during the comment period.
In response to one commenter's concern that the data appeared to be
a non-random sample of California gnatcatchers, the National Biological
Service (Newton, in litt. 1995) replied that although these are valid
concerns, they are not proof, as acknowledged by the commenter, that
Atwood's data are not representative. One commenting ornithologist who
was largely critical of Atwood's (1991) analyses nevertheless concluded
that ``[t]he data set gathered by Atwood was quite comprehensive and
included measurements from a large number of specimens throughout the
range of the species.'' In the Memorandum Opinion and Order filed May
2, 1994, the Court declared, citing the declaration of this
ornithologist, that ``it is not disputed that Atwood's means of
collecting data were proper.''
After noting the possible problem of the age of the specimen being
confounded with the collection site, the authors attempted to adjust
the data for year or month the data was collected. McDonald et al. (in
litt. 1994) removed specimens collected from May to September and thus
avoided problems associated with feather wear. Link and Pendleton (in
litt. 1994) adjusted several characters for month and year based on the
results of regression analyses. Messer (in litt. 1994) conducted two of
her analyses by limiting the specimens to those collected between 1920
and 1940, and 1980 to 1984. Link and Pendleton (in litt. 1994) were
cautious and indicated that they may not have removed all of the
confounding effects; however, they also indicated that they may have
over adjusted the data and removed differences due to sites.
After adjusting the data for year and month of collection, Link and
Pendleton (in litt. 1994) obtained results similar to the unadjusted
data. Messer (in litt. 1994) was able to classify the northern birds
from the southern birds using specimens collected from 1980 to 1984
correctly in 84 percent of the cases, and using birds collected from
1920 to 1940 in 94 percent of the cases. The results of McDonald et al.
(in litt. 1994) also yielded weak evidence of a break at 30 deg. north
latitude, even though they had removed birds collected during certain
months of the year. Atwood (in litt. 1994b) also had similar results
before and after he excluded the variable brightness of breast plumage
(a variable that would have changed as a specimen aged) from his
analysis.
Given the above considerations and results, the Service finds no
justification or cause for concluding that Atwood's data were
incomplete, censored, or otherwise inadequate. Further, the Service
concludes that the available information does not support the
hypothesis that the confounding of variables is responsible for
erroneous conclusions regarding perceived breaks in the morphology of
the coastal California gnatcatcher. The Service concludes that the
analysts took adequate care to remove the possible effects of
confounding of age of specimen and collection area.
Issue 4: The Service received four significant analyses and a
number of critiques of each of the analyses of Atwood's data. Each
commenter [[Page 15696]] attempted to answer a different question, and
consequently, each of the analyses used somewhat different statistical
techniques, and drew somewhat different conclusions. Some of the
commenters concluded that the clinal nature of the data would argue
against subspecies; or that a primary break occurs further south and
would argue that if there are subspecies, the boundary line should be
drawn further south in Baja California. Others argued that the data are
clumped (consistent with a subspecific break); or that the birds north
of 30 deg. north latitude are different from the birds south of 30 deg.
north latitude. The Service analyzed these reports to draw a conclusion
regarding whether the data support Atwood's 1991 conclusions.
Service Response: Several commenters produced new analyses of the
data provided by Atwood. Atwood (in litt. 1994b) also provided an
additional taxonomic analysis of the data. With the exception of Atwood
(in litt. 1994b), all of the authors (Messer in litt. 1994, Link and
Pendleton in litt. 1994, and McDonald et al. in litt. 1994) explicitly
stated that their expertise is in statistics, and that taxonomic
conclusions should be left to taxonomists. The Service has carefully
reviewed each of these analyses and critiques to examine the strengths
and the weaknesses of each approach. A summary of these analyses
follows.
Atwood (in litt. 1994b) presented a reanalysis of his data using
log10 transformations of 6 variables (bill length, tarsus length,
wing length, tail length, length of white spot on a tail feather
(retrix 6), and brightness of breast plumage). In one analysis, he
excluded the variable ``brightness of breast plumage'' because Mellink
and Rea (1994) found readings inconsistent, even when resampling a
single specimen. Atwood used a Tukey-Kramer method to conduct pairwise
comparisons of the sample area means. He also conducted a principal
components analysis (a method of determining how the data are
intercorrelated, and reducing intercorrelated data to a principal
component score) of the data and performed a cluster analysis on the
first two principal component scores as well as on the original
variables. Tail length, tail spot length, and brightness of breast
plumage varied significantly among sample areas (all P<0.001), and
multiple comparison tests revealed a grouping, or ``step,'' at 30 deg.
north latitude. The cluster analyses grouped sites north of 30 deg.
north latitude together, and variously grouped sites to the south.
Atwood's methods show that regional means may be clumped, but do not
show whether individual birds can be placed correctly into these
groups.
Link and Pendleton (in litt. 1994) used regression analysis of mean
latitudes of Atwood's (1991) nine sample areas against 25 characters.
They determined that the data vary along a geographic gradient. Link
and Pendleton (in litt. 1994) then conducted a series of tests to
determine if the characters were representative of gradual change or of
groupings. They used multivariate analysis of variance (MANOVA) to
place the original 9 sites into the best groupings of 8 sites, 7 sites,
6 sites, 5 sites, 4 sites, 3 sites and 2 sites. Abbott et al. (1985),
in their book on taxonomic analysis, recommended the use of canonical
variate analysis (MANOVAs) for delineation of subspecies, where the
data are continuous and the data are preclassified into postulated
groups. Akaike's information criterion (AIC) was used by Link and
Pendleton (in litt. 1994) to determine which grouping best fit the
data. Link and Pendleton (in litt. 1994) conducted discriminant
function analysis to determine if they could correctly classify birds
into groups. Hotelling's t2 test was used to test the significance
of the results. Cluster analysis and discriminant coordinates were
computed on the individual specimens to see how the data was clumped.
Finally, they attempted to adjust the data for time effects (see issue
3 above).
Link and Pendleton (in litt. 1994) obtained similar results in each
of these tests. They concluded that the changes in the characters are
more representative of groupings than of gradual change. They
determined that, at least one break occurs north of site 5 (mean
latitude of site 5 is 29.5 deg. north latitude) and at least one break
occurs south of site 5. The use of MANOVA would reduce the likelihood
of Type 1 error (reporting differences that do not exist) that would
occur if you looked at each variable separately. The AIC is not prone
to overfitting, and can be used to determine the model that best fits
the data. The AIC does not have an associated statistical test for
significance, and therefore, the groups identified in this manner may
not represent actual groupings (Newton in litt. 1995). Though Newton
(in litt. 1995) also indicated that Atwood's (in litt. 1994b) cluster
analysis would have been more useful if he had used individual
specimens rather than group means, Link and Pendleton's (in litt. 1994)
cluster analysis did use individual specimens and yielded groups
similar to their MANOVA results, creating a stronger basis for their
conclusions.
Messer (in litt. 1994) examined whether the birds north of 30 deg.
north latitude can be distinguished from the birds south of 30 deg.
north latitude. She used multivariate discriminant analysis to classify
birds into northern and southern subgroups with the boundary set at
30 deg. north latitude. Discriminant analysis is used when one is
examining a categorical dependent variable (e.g., north or south of
30 deg. north or one of 9 sites) and metric independent variables
(e.g., measurements of gnatcatcher characteristics). Discriminant
analysis would test whether the means among groups are equal. Using
several subsets of the data (e.g., limiting years of collection to
remove time effects, or in developing a model with one set of data and
another to test the model), Messer (in litt. 1994) concluded that one
could correctly classify the birds as being from the northern or
southern areas with 86 to 92 percent accuracy.
McDonald et al. (in litt. 1994) conducted their analyses using
individual specimens, and estimated the latitude based upon the
locality description given by Atwood in his original data set. They
removed specimens collected from May through September to avoid data
problems due to feather wear and molting, and attempted to adjust some
data for year of collection. To examine how the data are
intercorrelated, they conducted principal components analysis on size,
color, and pattern variables separately. McDonald et al. (in litt.
1994) conducted Gabriel's sum of squares simultaneous test procedure on
the first principal component scores and on the original variables.
McDonald et al. (in litt. 1994) conducted an intervention analysis to
look for steps or breaks in the trends in means. In addition, they
conducted a discriminant function analysis to determine whether birds
could be correctly classified at various latitudes.
The results from the Gabriel's test indicated that there were
significant differences in means of the first principal component at
24 deg. north latitude, and that for some of the size variables there
was weak evidence for a trend in means at 28 deg. north latitude or
27 deg. north latitude. There was weak evidence for difference in the
means at 30.5 deg. north latitude for the first principal component for
color variables. The intervention analysis revealed a significant rate
of change for 4 of the 16 individual size variables (page 6) at 30 deg.
north latitude (P< 0.10). The discriminant function analysis revealed
that the lowest misclassification rate was at 24 deg. north latitude (4
percent). The misclassification rate at 30 deg. north latitude was 13
percent (a 25 percent [[Page 15697]] misclassification rate is
generally acceptable for many subspecific groups).
McDonald et al. (in litt. 1994) used principal components analysis
(a method to reduce intercorrelated data to a single principal
component score) on size, color, and pattern variables separately. This
analysis may have been done to group data by measurement type (e.g.,
units of length, weight, etc.), as is recommended in some statistics
books (Newton in litt. 1995). Other statistics texts (e.g., Hair et al.
1995) apparently do not recommend grouping like measurements. A more
exhaustive approach to principal components analysis would have been to
do the analysis on all variables simultaneously, then exclude size
variables, then pattern variables, and so forth (Newton pers. comm.
1995). In that manner, McDonald et al. may have detected additional
intercorrelations among gnatcatcher characteristics.
McDonald et al. (in litt. 1994) presented a stronger case for
breaks in characters south of 30 deg. north latitude than they did for
characters found at 30 deg. north latitude. Atwood (1991, in litt.
1994), and Link and Pendleton (in litt. 1994) also found breaks south
of 30 deg. north latitude. The evidence of at least one break south of
30 deg. north is supportive of Atwood's (1991) conclusion of an
additional subspecific break. McDonald et al. (in litt. 1994) provided
the strongest evidence against Atwood's (1991) conclusions.
Nonetheless, they found weak statistical results supporting a break at
30 deg. north latitude (Gabriel's SS-STP and intervention analysis).
They also acknowledged that Gabriel's test may not have detected
differences in the critical region, where Atwood concluded changes
occur, because this test is sensitive to small sample sizes (i.e., an
investigator needs a large number of individual records before the test
will detect differences). Thus, in this portion of the analysis of
McDonald et al., the possibility of a Type 2 error or accepting the
null hypothesis when it should be rejected (i.e., believing that there
is no break in characters when in fact one does occur) was higher than
the possibility of a Type 1 error or rejecting the null hypothesis when
it should be accepted (i.e., believing that there is a break in
characters, when in fact no break exists).
McDonald et al. (in litt. 1994) also used ``intervention
analysis'', a procedure normally used when an experimenter intervenes
in some way (i.e., provides medical treatment) and wants to evaluate
whether changes in behavior or performance are statistically
significant (Edgington 1987). McDonald et al. (in litt. 1994)
apparently used this approach to see if changes at various latitudes
resulted in a sharp step. McDonald et al. (in litt. 1994) provided
limited details of this method, which they modified and ``tested using
data from the literature.'' Therefore, the Service was unable to fully
evaluate this method, which apparently is not commonly used. Messer (in
litt. 1995), however, indicated that the technique is a ``nonparametric
(and thus less powerful) version of linear regression analysis.''
McDonald et al. (in litt. 1994) did find weak statistical evidence
for a break in characters at 30 deg. north latitude, and were able to
distinguish the birds north and south of this line with a 13 percent
error rate. In evaluating their techniques, the Service notes that
McDonald et al. (in litt. 1994) used techniques that were less
exhaustive, or that were less well known, or that may have been more
likely to result in a Type 2 than in a Type 1 error than techniques
used by the other authors. The techniques of McDonald et al. (in litt.
1994) appeared more likely to accept the null hypothesis (e.g., there
is no subspecific break in gnatcatchers at about 30 deg. north
latitude). Given the selection of statistical techniques by McDonald et
al. (in litt. 1994), and that Atwood (in litt. 1994), Link and
Pendleton (in litt 1994), and Messer (in litt. 1994) found evidence for
a break at 30 deg. north latitude, the Service concludes that the weak
statistical evidence of a break at 30 deg. north latitude presented by
McDonald et al. should be given greater credence.
In summary, the MANOVA conducted by Link and Pendleton (in litt.
1994) and cluster analysis conducted by Atwood (in litt. 1994) are
supportive of groupings of birds rather than a cline. Use of cluster
analysis by Link and Pendleton (in litt. 1994) on individual specimens
provides stronger evidence that groups or ``steps'' exist in
characters. In addition, efforts by McDonald et al. (in litt. 1994) and
Messer (in litt. 1994) to determine correct classification rates
provide further evidence that gnatcatcher variance along a geographic
gradient is more indicative of groupings than of a gradual cline. The
misclassification rates at 30 deg. north latitude were well within the
range acceptable for subspecies.
Each author utilized different statistical methods to analyze the
data and draw conclusions. As a first step, the authors investigated
whether they could separate the means among various groupings of the
data. Atwood (in litt. 1994b) used a Tukey-Kramer multiple comparison
procedure to determine if the means of individual variables among
previously selected groups could be separated. Link and Pendleton (in
litt. 1994) used Hotelling's t2 on the groupings identified in
their MANOVA analysis to determine if the means could be separated.
McDonald et al. (in litt. 1994) used Gabriel's method to determine
differences in means at selected latitudes. Each of these approaches
was successful in separating means among groups of gnatcatchers.
The investigators next examined whether there might be steps in
these changes, or whether one could correctly classify (or place) the
birds within these groups. Messer (in litt. 1994) conducted a
multivariate discriminant analysis and found that the birds could be
classified into a groups north and south of 30 deg. north latitude with
an error rate of about 10 percent. Link and Pendleton (in litt. 1994)
conducted a clustering analysis to group individual specimens into
clusters and examined the overlap between the clusters and the
groupings identified in the MANOVA. McDonald et al. (in litt. 1994)
conducted a discriminant function analysis to identify latitudes that
separate the range of the bird into 2 groups with minimal
misclassification rates. Each of these approaches showed a break in the
characters at 30 deg. north latitude, and was supportive of Atwood's
(1991) conclusions.
In a statistically pure sense, these methods are exploratory in
nature and were useful in identifying hypotheses that could be tested
with respect to the gnatcatcher. To formally test these hypotheses, an
investigator would need to make similar measurements on newly gathered
gnatcatcher specimens. Issue 5 below discusses the Service's response
to this point. However, it is important to understand that statistics
are a tool used to assist an investigator in drawing conclusions in
that they can help quantify uncertainties with respect to those
conclusions (Newton pers. comm. 1995). The investigator still needs to
evaluate the practical significance of results, and should not focus
exclusively on statistical significance (Abbott et al. 1985, Hair et
al. 1995, Mayr et al. 1953). Statistics do not remove or supplant the
need to make informed decisions with respect to any data set. Messer
(in litt 1994), Link and Pendleton (in litt. 1994), and McDonald et al.
(in litt. 1994) all explicitly recognized that taxonomic decisions
should be made by taxonomists.
The misclassification rates identified by Messer (in litt. 1994)
and McDonald et al. (in litt. 1994), and the overlap in many of the
characters show that these [[Page 15698]] groupings of gnatcatchers are
not entirely discrete. Abbott et al. (1985) noted that taxonomists
expect ``variation within species to involve either a continuum or at
least some continuity or overlapping between forms.'' If the groupings
of California gnatcatcher were entirely discrete, avian taxonomists
likely would have assigned these groupings to separate species. Mayr
(1970) defined subspecies as ``an aggregate of phenotypically similar
populations of a species inhabiting a geographic subdivision of the
range of a species and differing taxonomically from other populations
of the species.'' Mayr (1970) concluded that the magnitude of taxonomic
difference necessary to appropriately decide when subspecies should be
delimited ``can be determined only by agreement among working
taxonomists.''
Grinnell (1926), Phillips (1991), and Atwood (1991) identified
30 deg. north latitude as a boundary between Polioptila californica
(=melanura) subspecies. Recent work suggests that the southern boundary
of P. c. californica may be further north, near the international
boundary between the United States and Mexico (Mellink and Rea 1994).
Mellink and Rea (1994) placed the birds between the international
border and 30 deg. north latitude in a new subspecies. Atwood
identified another subspecific break south of 30 deg. north. McDonald
et al. (in litt. 1994) and Link and Pendleton (in litt. 1994) also
noted a break south of 30 deg. north latitude, consistent with Atwood's
(1991) conclusion of an additional subspecific break. The consensus
among working taxonomists supports recognition of P. c. californica,
albeit its range may be more restricted than that proposed by Atwood
(1991). Therefore, the Service concludes that a finding that 30 deg.
north latitude as the southern specific boundary of P. c. californica
is supported by the available scientific evidence. Until additional
taxonomic work is published and accepted by the ornithological
community, the Service will recognize 30 deg. north latitude as the
southern subspecific boundary of P. c. californica.
Issue 5: Several commenters stated that analyses of a newly
collected independent data sets should be done to clarify gnatcatcher
taxonomy or resolve differences of opinion among the various
commenters. One commenter urged the Service to ``dismiss the subspecies
issue for gnatcatchers (pending further study) and focus on the
management of U.S. populations.'' Another commenter concluded that ``a
rigorous analysis of both morphometric, reflectance, genetic, and other
chemical data are required to address the problem in the clearest
possible manner.'' Other commenters added that the gnatcatcher should
not be listed until the perceived taxonomic controversy is resolved.
Service Response: The Service fully endorses and encourages efforts
to assess and refine the taxonomic status of all species, including the
coastal California gnatcatcher, provided that any collection of
specimens associated with such efforts does not result in unacceptable
mortality or other impacts. However, in making listing determinations,
section 4(b) of the Act requires the Service to make its listing
decisions within set timeframes and requires the Service to base its
listing decisions on the best scientific and commercial data available
at the time of the decision. The Service is not authorized to delay
listing decisions until all studies of arguable utility are completed,
until scientific debate is exhausted, or until complete consensus
occurs. The Service cannot await the ``next study,'' which may or may
not occur and which may or may not be affirmed by the scientific
community through the appropriate peer review process.
Efforts to conduct further analysis on the taxonomy and subspecific
limits of the California gnatcatcher would be costly and time
consuming. One could seek additional museum records not analyzed by
Atwood, or could collect new specimens. Collecting new specimens could
result in unacceptably high mortality. Moreover, collecting new field
specimens prior to making a final decision on this issue is not
practical. Alternatively, investigators could capture birds in mist
nets and obtain these measurements from live individuals, which would
then be released. However, additional researchers would be unable to
verify the results by visiting a museum and repeating the measurements.
As stated above under issue 4, the Service was charged with evaluating
whether Atwood's data supported his conclusions, and not with carrying
out additional studies to remove any and all controversy surrounding
the taxonomy of the Polioptila californica subspecies.
Conclusion
The Service has been charged with scrutinizing data and conclusions
rendered by Atwood, and determining if his data support his
conclusions. The Act provides that the Service must render its
determination on the basis of the best scientific and commercial data
available. The Service has made a concerted effort to obtain and
accurately assess the best scientific and best commercial information
available regarding the taxonomy and range of the coastal California
gnatcatcher. As an integral part of this process, the Service's
statutory mandates and standard scientific protocol require that we
recognize and act in accordance with the concepts, conventions, and
practices of the scientific method. To this end, the Service must seek
and seriously consider (1) data and analysis published in peer
reviewed, scientific journals, (2) the opinions of recognized experts
in given scientific disciplines, and (3) the input of the interested
public.
In this effort the Service has reviewed the analyses of the data
used by Atwood in his 1988 and 1991 papers. The Service finds that the
conclusions reached by Atwood (1991) are reasonable, and are generally
supported by the additional analyses received.
Under any circumstances that pertain to the taxonomy of North
American bird species, the Service actively seeks the publications,
input and expert opinion of the American Ornithologists' Union (AOU)
and its constituent Committee on Classification and Nomenclature
(Committee). The Committee and its publication (Check-list of North
American Birds) are recognized by the Service, scientists, and
scientific organizations throughout the world as authorities on avian
taxonomy in North America. Although the AOU has formally published its
positions on the taxonomy of the California gnatcatcher and coastal
California gnatcatcher (American Ornithologists' Union 1957, American
Ornithologists' Union 1989), the Service, nonetheless, made a concerted
effort to solicit and receive the recent, unequivocal, expert opinion
of the Committee and its members. During a past, prescribed public
comment period, the Service received responses from four members of the
Committee (including the Committee chair). The Committee members were
unanimous in acknowledging that Polioptila californica californica is
currently accepted as a distinct subspecies and that its southern
distributional limit occurs at 30 deg. north latitude.
In addition to independently seeking and reviewing the best
scientific information available from expert sources pertaining to the
taxonomic status of coastal California gnatcatcher, the Service also
repeatedly solicited comments or suggestions from the public, other
concerned governmental agencies, the scientific community, industry,
and any other party interested in gnatcatcher taxonomy and all other
aspects of the listing decision. In [[Page 15699]] response to these
requests for comments, the Service received a wide variety of public
comments and opinions, which are discussed earlier in this notice.
The Service has carefully considered all public comments received,
separate and independent analyses of Atwood's data, the National
Biological Service's (Link and Pendleton in litt. 1994) analysis of the
data, subsequent review of all technical submittals from the National
Biological Service (Newton in litt. 1995) and other interested parties,
the existing scientific literature, and the information presented in
the final listing rule designating the gnatcatcher as threatened (58 FR
16742). As a result, the Service concludes that the taxonomy and
geographic limits of the coastal California gnatcatcher are as provided
by Grinnell (1926, 1928) van Rossem (1931), American Ornithologists'
Union (1931), Grinnell and Miller (1944), Friedmann (1957), American
Ornithologists' Union (1957), Paynter (1964), Garrett and Dunn (1981),
Atwood (1991), and Phillips (1991). All of these scientific, peer
reviewed, publications present conclusions or affirmations that the
gnatcatcher (Polioptila californica californica) is restricted to
coastal southern California and northwestern Baja California, Mexico,
from Los Angeles County (and formerly Ventura County) south to the
vicinity of El Rosario at about 30 deg. north latitude.
The Service determines that the coastal California gnatcatcher is a
distinct taxon and that its geographic range is that described and
considered in the final listing rule for the coastal California
gnatcatcher (58 FR 16742). Therefore, the coastal California
gnatcatcher shall remain classified as a threatened species for reasons
that are stated in the final rule to list the species (58 FR 16742).
References Cited
A complete list of all references cited herein is available upon
request from the U.S. Fish and Wildlife Service, Carlsbad Field Office
(see ADDRESSES above).
List of Subjects in 50 CFR Part 17
Endangered and threatened species, Exports, Imports, Reporting and
recordkeeping requirements, and Transportation.
Authority: The authority for this action is the Endangered
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).
Authors
The primary authors of this notice are Loren R. Hays of the
Carlsbad Field Office (see ADDRESSES section), and Karla J. Kramer of
the U.S. Fish and Wildlife Service, Portland Regional Office, 911
Northeast 11th Ave., Portland, Oregon 97232-4181 (telephone 503/231-
6131).
Dated: March 22, 1995.
Mollie H. Beattie,
Director, U.S. Fish and Wildlife Service.
[FR Doc. 95-7549 Filed 3-23-95; 10:39 am]
BILLING CODE 4310-55-P