The purpose of this proposed revised critical habitat designation is: (1) To identify those geographic areas occupied at the time of listing that contain the physical or biological features essential to the conservation of the spotted owl; (2) to determine whether these features may require special management considerations or protection and provide general information on the types of management that may be appropriate consistent with the conservation of the owl; and (3) to identify any areas that may have been unoccupied at the time of listing, but that are nonetheless essential to the conservation and recovery of the owl. This proposed revised designation of critical habitat identifies all of the areas that we have initially determined meet the definition of critical habitat for the northern spotted owl. Federal lands comprise the strong majority of the area, but some State and private lands are also identified.

Under section 7(a)(2) of the Act, Federal agencies must, in consultation with and with the assistance of the Service, ensure that any action authorized, funded or carried out by that Federal agency is not likely to jeopardize the continued existence of a listed species (this is referred to as the “jeopardy standard”). Once finalized, the effect of designation of critical habitat for a listed species is to require that Federal agencies additionally ensure that their actions are not likely to result in the destruction or adverse modification of that critical habitat. In areas where northern spotted owls occur, including areas identified as meeting the definition of critical habitat in this proposed rule, Federal agencies such as the U.S. Forest Service and Bureau of Land Management are already consulting with the Service on the potential effects of their proposed actions under the “jeopardy standard,” regardless of whether these lands are currently designated as critical habitat. Aside from this requirement specific to Federal agencies, critical habitat designations do not provide additional regulatory protection for a species on non-Federal lands, unless the proposed activities involve Federal funding or permitting. In other words, designation of private or other non-Federal lands as critical habitat has no direct regulatory impact unless there is such a Federal connection. Although we anticipate that the effects on private landowners would not be significant, we acknowledge that there may be significant benefits to excluding private lands; we particularly request comments on whether and to what extent excluding such lands would be consistent with the Act.

While we have initially identified 13,962,449 ac (5,649,660 ha) of lands in the States of Washington, Oregon, and California that meet the definition of critical habitat for the northern spotted owl, it is important to emphasize that for several reasons, the number of acres actually included in the final designation may vary significantly from what is in this proposed revised designation. First, our conclusions as to what areas meet the Act's definition of “critical habitat” may change based on public comment and further analysis. Second, we may determine that military lands proposed for designation may qualify for an exemption from designation pursuant to section 4(a)(3)(B)(i) of the Act. Third, the Secretary may exclude certain areas from the final designation based on a thorough balancing analysis, including consideration of economic impacts, pursuant to section 4(b)(2) of the Act. In all cases, and without prejudging the consideration of further analysis and public comments, we anticipate a final designation that may be significantly smaller than the area currently identified.

The Act provides that critical habitat shall be designated after taking into consideration the economic impact, the impact on national security, and any other relevant impact of specifying any particular area as critical habitat. Section 4(b)(2) of the Act provides that the Secretary may exclude any area from critical habitat if he determines that the benefits of excluding that area outweigh the benefits of including it in the designation, unless such an exclusion would result in the extinction of the species. This “weighing” of considerations under section 4(b)(2) of the Act is the next step in the designation process, in which the Secretary may consider particular areas for exclusion from the final designation. In this proposed rule, we have already identified 4,571,672 ac (1,850,090 ha) of lands that we will specifically consider for exclusion from the final designation of critical habitat.

The final designation may reflect a variety of possible combinations of exclusions. The public is invited to comment on the possible exclusion of any areas proposed, but in particular those areas we have identified as those we propose to exclude and those we may additionally consider for exclusion from the final designation of critical habitat. After evaluating public comment and carefully analyzing and weighing all appropriate factors, a variety of potential outcomes are possible in the final designation.

This proposed revised critical habitat designation includes a diverse forest landscape that contains several different forest ecosystems and thousands of plant and animal species. Consistent with the best available science and the adaptive management principles outlined in the Revised Recovery Plan for the Northern Spotted Owl, we strongly encourage the application of ecosystem management principles and active forest management to ensure the long-term conservation of the northern spotted owl and its habitat, as well as other species dependent on these shared ecosystems. While proposed Federal actions must comply with requirements of the Act, actions with some short-term adverse impacts to spotted owls and critical habitat, but whose effect is to conserve or restore natural ecological processes and enhance forest resilience in the long term, should generally be consistent with the goals of critical habitat management. These management approaches are intended to be consistent with the principles of Executive Order 13563, which, as noted, directs agencies to consider regulatory approaches that reduce burdens and maintain flexibility and freedom of choice for the public. E.O. 13563 also further emphasizes that the rulemaking process must allow for public participation and an open exchange of ideas. To the extent feasible and consistent with law, the Service will seek to ensure that the process of designating critical habitat for the Northern Spotted Owl will be based on the open exchange of information and perspectives among State, local, and tribal officials, experts in relevant disciplines, affected stakeholders in the private sector, and the public as a whole.

The northern spotted owl (also variously referred to as simply “spotted owl” or “owl” in this document) was originally listed as threatened under the Act because of loss of its older growth forest habitat and a declining population (55 FR 26114, June 26, 1990). More recently, competition with barred owls ( Strix varia ) has emerged as a significant additional threat to spotted owl conservation. Experimental management of the barred owl threat is being addressed through a separate decision making process, as discussed further below.

One requirement of the Act, under section 7(a)(2), is that Federal agencies must, in consultation with and with the assistance of the Service, ensure that any action authorized, funded or carried out by that Federal agency is not likely to jeopardize the continued existence of a listed species (this is referred to as the “jeopardy standard”). Once finalized, the effect of designation of critical habitat for a listed species is to add an independent requirement that Federal agencies ensure that their actions are not likely to result in the destruction or adverse modification of that critical habitat. Thus, in areas where northern spotted owls occur, including most areas included in this proposed rule, Federal agencies such as the U.S. Forest Service (USFS) and Bureau of Land Management (BLM) are already consulting with the Service on the potential effects of their proposed actions under the “jeopardy standard,” regardless of whether these lands are currently designated as critical habitat. Aside from this requirement specific to Federal agencies, critical habitat designations do not provide additional regulatory protection for a species on non-Federal lands, unless the activities proposed involve Federal funding or permitting. In other words, designation of private or other non-Federal lands as critical habitat has no direct regulatory impact on the use of that land unless there is such a Federal connection. Identifying non-Federal lands that are essential to the conservation of a species may nonetheless be relevant, in that it alerts State and local government agencies and private landowners to the value of the habitat, and may help facilitate voluntary conservation partnerships such as Safe Harbor Agreements and Habitat Conservation Plans that may contribute to the recovery and delisting of the species.

To comply with the statutory requirements of the Act, we begin by identifying the areas that meet the definition of “critical habitat.” Notably, however, section 4 of the Act also requires us to consider the economic impacts, impacts on national security, and other relevant impacts of specifying any particular areas as critical habitat before we make our final designation. This process is summarized below in the section An Introductory Background of the Critical Habitat Process, and is detailed in the Exclusions section of this document.

In general, we recommend that critical habitat for the northern spotted owl should follow these basic management recommendations (detailed further in the Revised Recovery Plan for the Northern Spotted Owl, USFWS 2011; hereafter “Revised Recovery Plan”):

1. Conserve the older growth, high quality and occupied forest habitat as necessary to meet recovery goals.

2. Implement science-based, active vegetation management to restore forest health, especially in drier forests in the eastern and southern portions of the owl's range.

3. Encourage landscape-level planning and vegetation management that allow historical ecological processes, such as characteristic fire regimes and natural forest succession, to occur on these landscapes throughout the range of the owl. This approach has the best chance of resulting in forests that are resilient to future changes that may arise due to climate change.

These general recommendations are consistent with the underlying purpose of the Act. Section 2(b) of the Act states, in part: “The purposes of this Act are to provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved.” A fundamental goal of critical habitat management is not only to conserve the listed species, but also to conserve the ecosystem upon which that species depends. This is the case with the northern spotted owl.

An “ecosystem” is a biological community of interacting organisms and their physical environment, or as the complex of a community of organisms and its environment functioning as an ecological unit (Krebs 1972, pp. 10-11; Ricklefs 1979, pp. 31-32, 869). These ecosystem interactions and functions are often referred to as ecological “relationships” or “processes.” Thus, to conserve the northern spotted owl as directed by the Act, one must also conserve the ecological processes that occur within the ecological landscape inhabited by the species. These natural processes—such as vegetation succession, forest fire regimes, and nutrient cycling—create and shape the physical and biological features that form the foundation of critical habitat. A complex interaction of physical and biological factors contribute to the development and maintenance of these ecosystems, which in turn provide the northern spotted owl with the environmental conditions required for its conservation and survival. A fundamental goal of critical habitat management should thus be to understand, describe, and conserve these processes. This “ecosystem approach” of management will ultimately have the highest likelihood of conserving listed species such as the northern spotted owl in the long term (Knight 1998, p. 43).

Service policy also endorses this approach: “Species will be conserved best not by a species-by-species approach but by an ecosystem conservation strategy that transcends individual species” (59 FR 34724, July 1, 1994). The Service considers this ecosystem approach in critical habitat designations for other listed species (e.g., in Hawaii (75 FR 18960, April 13, 2010; 76 FR 46362, August 2, 2011)). Likewise, the U.S. Forest Service, which manages the great majority of the proposed revised areas initially meeting the definition of northern spotted owl critical habitat, has prioritized restoring and maintaining natural ecological function and resiliency to its forest lands (Blate et al. 2009, entire; USDA 2010, entire; Tidwell 2011, entire). Active management of critical habitat is intended to be fully compatible and consistent with these landscape-level ecosystem conservation efforts.

This proposed revised critical habitat designation includes a diverse forest landscape that contains several different forest ecosystems and thousands of plant and animal species. It ranges from dry, fire-prone forests to moist old-growth conifer forest to a mix of conifers and hardwood trees. Thousands of species occur in these forest ecosystems, including other listed species with very specific biological needs. Prescribed management for all of these needs at the species level on large landscapes will raise a number of challenges (Thompson et al. 2009, p. 29). Many scientists believe a single-species approach to forest management is limited and that land managers need to focus on broader landscape goals that address ecosystem process and future habitat conditions (see, e.g., Thomas et al. 2006, p. 286; Boyd et al. 2008, p. 42; Hobbs et al. 2010, p. 487; Mori 2011, pp. 289-290). We strongly encourage the application of ecosystem management principles and active forest management to ensure the long-term conservation of the northern spotted owl and its habitat, as well as other species dependent on these shared ecosystems.

Another important development that would inform spotted owl critical habitat management involves changes in forestry science. Emulating natural disturbance regimes is emerging as a dominant paradigm in North American forest management (Seymour and Hunter 1999, p. 56; Long 2009, p. 1868). This change is occurring in response to (1) the simplification of forests in terms of structure, age-class diversity, and species composition as a result of management for timber production and (2) a recognition of fundamental changes in ecosystem function and processes due to land management practices, especially fire and successional patterns (Franklin et al. 2002, pp. 402-408; Hessburg et al. 2005, pp. 134-135; Drever et al. 2006, p. 2291). Although active vegetation management is unlikely to precisely mimic natural forest disturbance in all ways, it can be used to better maintain the resilience of landscapes and wildlife populations to respond to natural disturbance and climate change (Lindenmayer et al. 2008, p. 87). In general, silviculture prescriptions that apply ecological forestry principles to address the conservation of broader ecological processes are compatible with maintaining the proposed critical habitat's essential features in the long term (USFWS 2011, p. III-14).

Explicitly prescribing such management at a fine scale (e.g., forest stand level) is beyond the scope of this document and should be developed at the appropriate land management unit (e.g., National Forest or BLM District; USDA 2010, entire) and through consultation with the Service, as appropriate. While proposed Federal actions must comply with requirements of section 7 of the Act, which requires consideration of short as well as long-term impacts to species and their critical habitat, as described below and in the Revised Recovery Plan, management actions with some short term adverse impacts to spotted owls and critical habitat, but whose effect is to conserve or restore natural ecological processes and enhance forest resilience in the long term, should generally be consistent with the goals of critical habitat management (USFWS 2011, p. III 11-39). The Service has recently approved these types of management actions in occupied spotted owl habitat on BLM and USFS lands.

Specific considerations for managing within spotted owl critical habitat are discussed in more detail in the Special Management Considerations and Adverse Modification sections later in this document. In sum, vegetation and fuels management in dry and mixed-dry forests is strongly encouraged both within and outside designated critical habitat where the effect of such treatment is to conserve natural ecological processes or restore them (including fire) where they have been modified or suppressed (Allen et al. 2002, pp. 1429-1430; Spies et al. 2006, pp. 358-361; Fielder et al. 2007, entire; Prather et al. 2008, entire; Lindenmayer et al. 2009, p. 274; Tidwell 2011, entire). Likewise, in moist and some mixed forests, management of spotted owl critical habitat should be compatible with broader ecological goals, such as the retention of high-quality older forest, the continued treatment of young or homogenous forest plantations, and the conservation or restoration of complex early seral forest habitat (Spies et al. 2007b, pp. 57-63; Betts et al. 2010, pp. 2117, 2126-2127; Swanson et al. 2010, entire). In general, actions that promote ecological restoration and those that apply ecological forestry principles as described in the Revised Recovery Plan (USFWS 2011, pp. III-11 to III-41) and later in this document are likely to be consistent with the conservation of the northern spotted owl and the management of its critical habitat.

In conclusion, the designation and management of critical habitat for the spotted owl must be compatible with these broader landscape management goals if it is to conserve the spotted owl as required by the Act. It is therefore important to emphasize that spotted owl critical habitat should not be a “hands off” reserve in the traditional sense. Rather, it should be a “hands on” ecosystem management landscape that should include a mix of active and passive actions to meet a variety of forest conservation goals that support long-term spotted owl conservation. It would be inconsistent with the stated purposes of the Act, the Revised Recovery Plan (USFWS 2011), and the goals of the Northwest Forest Plan (NWFP) if spotted owl critical habitat was narrowly managed and, in so doing, discouraged land managers from implementing scientifically justified measures for conserving forest ecosystem functions and health.

Section 4(a)(3) of the Act specifies that the Service shall designate critical habitat for endangered or threatened species and may, from time-time thereafter as appropriate, revise such designation. Critical habitat is defined as (1) specific areas within the geographical area occupied by the species at the time it is listed, on which are found those physical or biological features that are essential to the conservation of the listed species and which may require special management considerations or protection, and (2) specific areas outside the geographical area occupied by the species at the time it is listed that are essential for the conservation of a listed species. Our regulations direct us to focus on the “primary constituent elements,” or PCEs, in identifying these physical or biological features.

As part of our rulemaking process, we identify what types of activities on Federal lands, or what activities involving a Federal nexus, may be affected within the proposed critical habitat area and would require consultation under section 7(a)(2) of the Act. Although we are in the process of developing an economic analysis specific to this proposed revision of critical habitat, the economic analysis for the 2008 designation of critical habitat for the northern spotted owl may be informative in terms of providing the categories of activities identified as those that may be affected within critical habitat. For the 2008 critical habitat, those initially included: (1) Timber management, (2) barred owl management and control, (3) northern spotted owl surveys and monitoring, (4) fire management, (5) linear projects (i.e., transportation, pipelines, and powerlines), (6) restoration, and (7) recreation. However, the effects on fire management, linear projects, restoration, and recreation were found to range from minimal to none. As a consequence, the 2008 economic analysis concluded that there were four categories of potential impacts from critical habitat for the northern spotted owl: (1) Impacts to timber management; (2) impacts to survey and monitoring activities; (3) impacts to barred owl management; and (4) costs related to consultations under section 7 of the Act.

Some specific examples of timber management and commercial timber harvesting activities that may be affected by the designation of critical habitat include, but are not limited to: Traditional clearcutting; targeted variable retention harvest; pre-commercial or commercial thinning; variable thinning in single-story, uniform forest stands; reduction of fuels in order to reduce the effect of wildfires; hazard tree removal; removal of younger, shade-intolerant conifers to reduce competition with larger, legacy conifers; and silvicultural treatments. Some of these activities may have short-term negative impacts to the owl, but long-term benefits by creating higher quality habitat. These activities and possible effects are discussed below in more detail (see Effects of Critical Habitat Designation, Section 7 Consultation ). As described in this proposed rule, we anticipate that, in general, actions that promote ecological restoration and those that apply ecological forestry principles as described in the Revised Recovery Plan (USFWS 2011, pp. III-11 to III-41) and later in this document are likely to be consistent with the conservation of the northern spotted owl and the management of its critical habitat.

Any proposed designation of critical habitat begins with the identification of all specific areas that contain the physical or biological features essential to the conservation of the species and which may require special management considerations or protection (this applies to areas occupied at the time of listing), and all areas that the Secretary has otherwise determined to be essential to the conservation of the species (this applies to areas unoccupied by the species at the time of listing). The initial identification of these lands is based on the best available scientific information. After we have identified the lands that meet the definition of “critical habitat,” we consider the potential economic, national security, or other relevant impacts of the designation. Under section 4(b)(2) of the Act, we may identify any lands for which we believe the benefits of exclusion may outweigh the benefits of inclusion, and solicit public comment on our consideration of those particular lands for exclusion or exemption from the final designation, as we have done in this proposed rule.

In addition, section 4(a)(3)(B)(i) of the Act species that the Secretary shall not designate any lands as critical habitat owned or controlled by the Department of Defense, or designated for its use, that are subject to an integrated natural resources management plan (INRMP) if the Secretary determines in writing that such plan provides a benefit to the species for which critical habitat is proposed for designation. Such lands may be exempted from the designation of critical habitat, which is a separate process from the exclusion of lands under section 4(b)(2) of the Act.

For this proposed revised designation of critical habitat for the northern spotted owl, we used the integrated habitat conservation planning framework developed in the Revised Recovery Plan for the Northern Spotted Owl (USFWS 2011, Appendix C) as one key source of information. This framework integrates a spotted owl habitat model, a habitat conservation planning model, and a population simulation model that collectively allowed us to compare estimated spotted owl population performance among alternative habitat conservation network scenarios under a variety of potential conditions. This process specifically incorporated consideration of the physical or biological features and allowed us to determine the quantity and distribution or spatial arrangement of these features that are essential to the conservation of the northern spotted owl. It also assisted us in identifying habitat that may have been unoccupied at the time of listing but is essential to the species' conservation. Additionally, it allowed us to consider the effect of variables such as habitat change over time and density of barred owls, as well as to evaluate the effect of including different configurations of landownership in the scenarios considered.

Consistent with our statutory obligation to consider the best available science in making decisions, our evaluation of spotted owl population performance, based on various habitat configurations tested, required that we make assumptions regarding some of the model inputs, for example the interaction rate between northern spotted owls and barred owls (all assumptions are explicitly identified in Dunk et al. 2012). Given that critical habitat cannot be expected to ameliorate non-habitat based stressors to spotted owl populations, it was necessary to establish reasonable assumptions regarding barred owl encounter rates (the probability that a given spotted owl territory also has barred owls present) that we believed could, along with critical habitat designation, lead to recovery of the northern spotted owl. Absent such an assumption, it would not be possible to identify those areas essential to the conservation of the owl, as the negative effect of barred owls would essentially mask the positive effect of habitat on spotted owl populations. Therefore, as part of the critical habitat modeling process, we established region-specific barred owl encounter rates based on preliminary analyses conducted as part of the modeling process (Dunk et al. 2012) and barred owl encounter probabilities estimated from long-term demographic study areas (Forsman et al. 2011) within each modeling region. In some areas, we maintained barred owl encounter rates at current levels or allowed them to increase slightly. In others, we used encounter rates that were less than current levels, but at levels we believed could potentially be maintained through management activities.

It is important to recognize that the barred owl encounter probabilities we established for modeling purposes do not represent predictions about conditions that will be achieved through management actions, or that they are an estimate of what is likely to occur in the future. Instead, the assumed barred owl encounter probabilities were used to identify the critical habitat that is essential to recovery of the northern spotted owl, assuming that other, non-habitat based threats to the species have been addressed. We invite public comment on the process we used to evaluate barred owl effects on critical habitat.

The Service is currently in the process of preparing an Environmental Impact Statement (EIS) that will serve as the basis for a decision on whether to move forward with a study on the experimental removal of barred owls. We will release the EIS for public review and comment in the near future. If we decide to proceed with this study, we will likely implement it over a period of approximately 4 to 10 years. Furthermore, if we decide to proceed with this experimental removal study, that decision will not include a determination on whether or how barred owls would be managed in the long term; we will make that decision only after further evaluation of the results from our initial study. Barred owls are already present across most, if not all, of the landscape being proposed as revised critical habitat, and in many cases both spotted owls and barred owls are occupying the same forest lands. By designating additional habitat distributed across the range of the subspecies, our goal is to increase the likelihood that spotted owls will be able to persist in areas where barred owls are also present. With regard to how possible future management of the barred owl could affect the need for critical habitat for the spotted owl, if, through experimental removal studies or otherwise, we learn how to manage barred owls for the benefit of spotted owls, and if such management efforts are undertaken and result in a reduction in the amount of habitat essential to the conservation of the northern spotted owl, the Service may at that point consider revising critical habitat.

Each of the three models used in our integrated conservation planning framework helped identify an important element of the statutory definition of critical habitat: The identification of physical or biological features needed by the northern spotted owl, and the distribution of those features across the geographical range of the species; and the identification of a landscape configuration where these features, as well as any necessary unoccupied areas, are essential to the conservation of the species. In all cases, we attempted to maximize reliance on public lands, looking first to Federal lands and secondarily to State lands, and incorporated private lands only when Federal and State lands were insufficient to meet the recovery needs of the species. We then evaluated the population performance of each habitat configuration considered against the recovery criteria as set forth in the Revised Recovery Plan for the Northern Spotted Owl (USFWS 2011, p. ix).

Following the application of the modeling framework, we further refined the model-based map units after considering land-ownership patterns, interagency coordination, and best professional judgment, with the objective of increasing the efficiency and effectiveness of the critical habitat proposal. We again used the population simulation model to evaluate whether the habitat network, as refined, continued to provide what is essential to the conservation of the northern spotted owl. The details of this process are presented in this proposed rule in the section “Criteria Used to Identify Critical Habitat,” and are provided in greater detail in our supporting document “Modeling and Analysis Procedures Used to Identify and Evaluate Potential Critical Habitat Networks for the Northern Spotted Owl,” (Dunk et al. 2012), available online at http://www.regulations.gov (see ADDRESSES ), or by contacting our Oregon Fish and Wildlife Office (see FOR FURTHER INFORMATION CONTACT ). The latter document in particular describes the specific assumptions and uncertainties associated with the modeling process, and we invite public comment on these assumptions and uncertainties. We further invite public comment on those areas we have identified here as providing the physical or biological features essential the conservation of the owl, or that have been otherwise determined to be essential to the conservation of the species.

As a result of this process, this proposed revised designation of critical habitat includes all of the areas that we have determined meet the definition of critical habitat for the northern spotted owl. Federal lands comprise the majority of the proposed revised designation, but some State and private lands are also identified. As required by section 4(b)(2) of the Act, we have used the best scientific data available to identify those areas within the geographical area occupied by the species at the time it was listed, on which are found those physical or biological features essential to the conservation of the species and which may require special management considerations or protection. In addition, the Secretary has determined that some areas in a small subset of the proposed revised designation may not have been occupied at the time of listing, but these areas are nevertheless essential to the conservation of the species. While we conclude that the vast majority of lands included in the proposed designation were occupied at the time of listing for the reasons discussed below, we also evaluated them as if they were not occupied and have tentatively determined that all of these lands are essential to the conservation of the species. Based on the standards of the Act and our implementing regulations, we have initially identified 13,962,449 acres (5,649,660 ha) of lands in the States of Washington, Oregon, and California that meet the definition of critical habitat for the northern spotted owl.

The specific areas actually included in the final designation may vary significantly from what is in this proposed revised designation for several reasons. First, our conclusions as to what areas meet the Act's definition of “critical habitat” may change based on public comment and further analysis. Second, we may determine that military lands proposed for designation may qualify for an exemption from designation pursuant to section 4(a)(3)(B) of the Act. As described below under “Exemptions,” Joint Base Lewis-McChord in the State of Washington is currently in the process of revising its INRMP, and is under consideration for exemption from the final designation of critical habitat. Third, the Secretary may exercise his discretion to exclude certain areas from the final designation based on a thorough balancing analysis pursuant to section 4(b)(2) of the Act. In all cases, we anticipate a final designation that may be smaller than the current proposed revised designation. The proposed revised designation may be taken as a maximum in the sense that, in no case, with the exception of minor boundary adjustments, would the final designation include lands not included in the proposed rule without first providing the opportunity for public notice and comments with respect to such additional lands.

As described above, the Act provides that critical habitat shall be designated after taking into consideration the economic impact, the impact on national security, and any other relevant impact of specifying any particular area as critical habitat. Section 4(b)(2) of the Act provides that the Secretary may exclude any area from critical habitat if he determines that the benefits of excluding that area outweigh the benefits of including it in the designation, unless such an exclusion would result in the extinction of the species. This “weighing” of considerations under section 4(b)(2) of the Act is the next step in the designation process, in which the Secretary may consider particular areas for exclusion from the final designation. In this proposed revised designation of critical habitat, we have already identified 4,571,672 ac (1,850,090 ha) of lands that we will consider for exclusion from the final designation of critical habitat. We note that Executive Order 13563 states that to the extent permitted by law, each agency must “tailor its regulations to impose the least burden on society, consistent with obtaining regulatory objectives,” and that each agency “shall identify and consider regulatory burdens that reduce burdens and maintain flexibility and freedom of choice for the public.”

The final designation may reflect a variety of possible combinations of exclusions (We note that in 1991, the initial proposal was for 11.6 million acres of critical habitat (May 6, 1991, 56 FR 20816), but the final rule identified 6.9 million acres (January 15, 1992, 57 FR 1796), a decrease of 40 percent). The public is invited to comment on the possible exclusion of any areas proposed, but in particular those areas we have identified as those we propose to exclude and those we may additionally consider to exclude from the final designation of critical habitat. After evaluating public comment and carefully analyzing and weighing all appropriate factors, a variety of potential outcomes is possible in the final designation. The following represents a range of some possible outcomes that may result from the critical habitat designation process. In all cases, and without prejudging the consideration of further analysis and public comments, we anticipate a final designation that may be significantly smaller than the currently identified area. We emphasize that these are possible outcomes and that we seek comments on alternatives, including those that may involve additional exclusions beyond those specifically identified in this proposal.

Possible Outcome 1. Finalize critical habitat on all lands described as meeting the definition of critical habitat in this proposed revised designation. This outcome would result if the Secretary determines, following public comment and consideration of all possible exclusions and exemptions, that all of the areas proposed as revised critical habitat still meet the definition of critical habitat, and no areas are excluded or exempted from the final designation. In this outcome, the final designation would be 13,962,449 ac (5,649,660 ha).

Possible Outcome 2. Finalize critical habitat by excluding all private and State lands with active conservation agreements (HCPS, SHAs, and other formal agreements) in place, identified here as proposed for exclusion based on a through balancing analysis under section 4(b)(2) of the Act (see Table 1). This outcome would result if, following public comment and consideration of all possible exclusions, the Secretary determined that, of all of the areas identified here for consideration for possible exclusion, the benefits of excluding those areas with formal conservation agreements that support conservation of the northern spotted owl would be greater than the benefits of including those areas in critical habitat, and if exclusion of those areas did not result in the extinction of the species. In this outcome, the final designation would be 13,025,633 ac (5,271,287 ha).

Possible Outcome 3. Finalize critical habitat by excluding all private and State lands with active conservation agreements (HCPs, SHAs, and other formal agreements) in place, all State parks, and all Congressionally reserved natural areas (e.g., wilderness areas, national scenic areas, national parks) based on a through balancing analysis under section 4(b)(2) of the Act (see Table 1). This outcome would result if, following public comment and consideration of all possible exclusions, the Secretary determined that of all of the areas identified here as proposed for exclusion, the benefits of excluding those areas with formal conservation agreements that support conservation of the northern spotted owl, as well as the benefits of excluding those State parks and Federal natural areas managed as parks or wilderness, would be greater than the benefits of including those areas in critical habitat, and if exclusion of those areas did not result in the extinction of the species. In this outcome, the final designation would be 10,229,121 ac (4,139,578 ha). Figures 1 through 3 demonstrate what the final critical habitat designation would be if all exclusions proposed in this proposed revised rule were finalized.

Possible Outcome 4. Finalize critical habitat by excluding all private lands, all State lands, and all Congressionally reserved natural areas based on a through balancing analysis under section 4(b)(2) of the Act (see Table 1). This outcome would result if, following public comment and consideration of all possible exclusions, the Secretary determined that of all of the areas identified here for consideration for possible exclusion, the benefits of excluding all private lands, State lands, and Federal natural areas managed as parks or wilderness would be greater than the benefits of including those areas in critical habitat. In this outcome, the final designation would be 9,390,777 ac (3,800,313 ha).

We emphasize that there may be significant benefits to excluding private lands; we particularly request comments on whether and to what extent excluding such lands would be consistent with the Act.

There is, of course, a Possible Outcome 5, which would involve greater exclusions than those identified in Possible Outcome 4. As noted, we request public comments on any such potential exclusions, and the underlying law and science that would support such exclusions. In considering the various possible outcomes, we will focus on the requirements of the Act and to the extent consistent with law, the requirements of Executive Order 13563 and in particular its emphasis on public participation, on imposing the least burden on society, and on maintaining flexibility and freedom of choice for the public.

We intend that any final action resulting from this proposed revised rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other concerned government agencies, the scientific community, industry, or any other interested party concerning this proposed rule. We particularly seek comments concerning:

(1) Specific information regarding:

(a) The amount and distribution of northern spotted owl habitat;

(b) What areas were occupied at the time of listing and contain features essential to the conservation of the species such that they should be included in the designation and why;

(c) Whether these essential features may require special management considerations or protection and what special management considerations or protection may be needed in critical habitat areas we are proposing;

(d) What areas not occupied at the time of listing are essential for the conservation of the species and why;

(e) Whether we have identified here any areas occupied at the time of listing, but that do not contain features essential to the conservation of the species, and that therefore should not be included in the designation; and

(f) Whether we have identified here any areas that may not have been occupied at the time of listing and that are not essential to the conservation of the species, such that they should not be included in the designation.

(2) Land-use designations and current or planned activities in the subject areas and their possible impacts on proposed critical habitat.

(3) Our proposed approach to effects determinations for the purposes of conducting consultation under section 7(a)(2) of the Act, in particular the application of a 500-ac (200-ha) scale as a screen for a determination of not likely to adversely affect, as described in the section Determinations of Adverse Effects and Application of the “Adverse Modification” Standard.

(4) Assistance in the identification of any private lands that are not expressly identified as intended for inclusion within critical habitat and that may have inadvertently been included within the designation, due to mapping and modeling limitations, as described in the section “Proposed Revised Critical Habitat Designation.”

(5) Information on the potential impacts of climate change on the northern spotted owl and proposed critical habitat, and whether special management needs or protections may be needed to address this issue in the critical habitat areas we are proposing.

(6) Any probable economic, national security, or other relevant impacts of designating any area as critical habitat, and in particular, any impacts on small entities, and the benefits of including or excluding areas that exhibit these impacts. We particularly request information and comments on what activities may occur and the effects to those activities in the proposed revised critical habitat areas. Such information could include:

(a) The extent of possible activities, including temporal and spatial scale, relative to the critical habitat area within which they occur.

(b) The impact of possible activities on the habitat's likelihood of serving its intended conservation function or purpose.

(c) The consistency of possible activities with the intent of the recovery plan or other landscape-level conservation plans.

(7) Whether the benefits of excluding the private and State lands with active conservation agreements (HCPs, SHAs, and other formal agreements) and Congressionally reserved natural areas (e.g., wilderness areas, national scenic areas, national parks) that are proposed for exclusion outweigh the benefits of including them in critical habitat.

(8) Whether the benefits of excluding any other particular area from critical habitat outweigh the benefits of including that area in critical habitat under section 4(b)(2) of the Act, after considering both the potential impacts and benefits of the proposed revised critical habitat designation. We are considering the possible exclusion of non-Federal lands, especially areas in private ownership, in particular, and whether the benefits of exclusion may outweigh the benefits of inclusion of those areas. We, therefore, request specific information on:

(a) The benefits of including any specific areas in the final designation and supporting rationale.

(b) The benefits of excluding any specific areas from the final designation and supporting rationale.

(c) Whether any specific exclusions may result in the extinction of the species and why (see Exclusions section, below).

(d) For private lands in particular, we are interested in information regarding the potential benefits of including private lands in critical habitat versus the benefits of excluding such lands from critical habitat. This information does not need to include a detailed technical analysis of the potential effects of designated critical habitat on private property. In weighing the potential benefits of exclusion versus inclusion of private lands, the Service may consider whether existing partnership agreements provide for the management of spotted owl habitat. We may consider, for example, the status of conservation efforts, the effectiveness of any conservation agreements to conserve the species, and the likelihood of the conservation agreement's future implementation. There may be broad public benefits of encouraging collaborative efforts and encouraging local and private conservation efforts, and these broad benefits are important considerations in our evaluation.

(9) Our process used for identifying those areas that meet the definition of critical habitat for the northern spotted owl, including the assumptions incorporated into the habitat modeling process, as described more fully in the section “Criteria Used to Identify Critical Habitat” and also in our supporting documentation (Dunk et al. 2012).

(10) Whether we could improve or modify our approach to designating critical habitat in any way to provide for greater public participation and understanding, or to better accommodate public concerns and comments.

(11) Specific information on ways to improve the clarity of this rule as it pertains to completion of consultations under section 7 of the Endangered Species Act.

Our final determination concerning the revision of northern spotted owl critical habitat will take into consideration all written comments and any additional information we receive during all comment periods. The comments will be included in the public record for this rulemaking, and we will fully consider them in the preparation of our final determination. On the basis of information received, we may, during the development of our final determination, find that areas within the proposed designation do not meet the definition of critical habitat, that some modifications to the described boundaries are appropriate, or that areas may or may not be appropriate for exclusion based on a through balancing analysis under section 4(b)(2) of the Act under section 4(b)(2) of the Act.

You may submit your comments and materials concerning this proposed rule by one of the methods listed in the ADDRESSES section. We will post your entire comment—including your personal identifying information—on http://www.regulations.gov. You may request at the top of your document that we withhold personal information such as your street address, phone number, or email address from public review; however, we cannot guarantee that we will be able to do so.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on http://www.regulations.gov, or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Oregon Fish and Wildlife Office (see FOR FURTHER INFORMATION CONTACT ).

It is our intent to discuss only those topics directly relevant to the revised designation of critical habitat in this proposed rule. For further details regarding northern spotted owl biology and habitat, population abundance and trend, distribution, demographic features, habitat use and conditions, threats, and conservation measures, please see the Northern Spotted Owl 5 year Review Summary and Evaluation, completed October 26, 2011, and the Revised Recovery Plan for the Northern Spotted Owl (USFWS 2011), completed July 1, 2011. Both of these documents are available on the U.S. Fish and Wildlife Service's Endangered Species web site at http://ecos.fws.gov/; under “Species Search,” enter “northern spotted owl”). As detailed below, Appendix C of the Revised Recovery Plan is particularly informative, as the habitat modeling process described therein was used to help identify those areas considered essential to the conservation of the northern spotted owl in this proposed revised designation of critical habitat. Furthermore, the recovery criteria for the northern spotted owl, as described in the Revised Recovery Plan (USFWS 2011, pp. I-1 to I-2), helped to discriminate between the various scenarios considered in the modeling process in terms of assessing which of the habitat networks evaluated would contribute most efficiently to the conservation of the northern spotted owl.

The Service recognizes that this proposed revision of critical habitat represents an increase in the total land area identified from previous designations in 1992 (January 15, 1992; 57 FR 1796) and 2008 (August 13, 2008; 73 FR 47325). For a detailed explanation of the changes proposed between this proposed revised designation and the present designation of critical habitat for the northern spotted owl, please see Summary of Changes from Previously Designated Critical Habitat, below.

The northern spotted owl inhabits structurally complex forests from southwestern British Columbia through Washington and Oregon to northern California. The northern spotted owl was listed under the Act as a threatened species in 1990 because of widespread loss of habitat across its range and the inadequacy of existing regulatory mechanisms to conserve it (55 FR 26114; June 26, 1990). Although the rate of loss of habitat due to timber harvest has been greatly reduced on Federal lands over the past two decades, both past and current habitat loss remain a threat to the northern spotted owl. Despite implementation of habitat conservation measures in the early 1990s, Thomas et al. (1990, p. 5) and USDI (1992, Appendix C) foresaw that owl populations would continue to decline for several decades, even with habitat conservation, as the consequence of lag effects at both individual and population levels. However, many populations of northern spotted owls have declined at a faster rate than anticipated, especially in the northern parts of the subspecies' range (Anthony et al. 2006, pp. 31-32; Forsman et al. 2011, pp. 65, 76). We now know that the suite of threats facing the northern spotted owl differs from those at the time it was listed; in addition to the effects of historical and ongoing habitat loss, the northern spotted owl faces a new significant and complex threat in the form of competition from the congeneric (referring to a member of the same genus) barred owl (USFWS 2011, pp. I-7 to I-8).

During the second half of the 20th century, barred owls expanded their range from eastern to western North America, and the range of the barred owl now completely overlaps that of the northern spotted owl (Gutiérrez et al. 1995, p. 3; Crozier et al. 2006, p. 761). Barred owls compete with northern spotted owls for habitat and resources for breeding, feeding, and sheltering, and the presence of barred owls has significant negative effects on northern spotted owl reproduction, survivorship, and successful occupation of territories (see “Population Status and Trends,” below). The loss of habitat has the potential to intensify competition with barred owls by reducing the total amount of resources available to the northern spotted owl and by increasing the likelihood and frequency of competitive interactions. Barred owls select very similar habitat to spotted owls for breeding, feeding, and sheltering, and loss of habitat has the potential to intensify competition between species. While conserving habitat will not alleviate the barred owl threat, Dugger et al. (2011, pp. 2464-2465) found that spotted owl occupancy and colonization rates decreased as both barred owl presence increased and available habitat decreased. These authors concluded that, similar to another case in which increased suitable habitat was required to support two potentially competing raptors, increased habitat protection for spotted owls may be necessary to provide for sustainable populations in the presence of barred owls (Dugger et al. 2011, p. 2467). Maintaining high-quality habitat has been important since the northern spotted owl was initially listed as threatened in 1990, and this competitive pressure from barred owls has intensified the need to conserve and restore large areas of contiguous, high-quality habitat across the range of the northern spotted owl (Dugger et al. 2011, p. 2464; Forsman et al. 2011, p. 76; USFWS 2011, Recovery Action 32 [RA32], p. III-67).

It is becoming increasingly evident that solely securing habitat will not be effective in achieving the recovery of the northern spotted owl when barred owls are present (USFWS 2011, p. vi). While conservation of high-quality habitat is essential for the recovery and conservation of the owl, habitat conservation alone is not sufficient to achieve recovery objectives. As stated in the Revised Recovery Plan, “addressing the threats associated with past and current habitat loss must be conducted simultaneously with addressing the threats from barred owls. Addressing the threat from habitat loss is relatively straightforward with predictable results. However, addressing a large-scale threat of one raptor on another, closely related raptor has many uncertainties” (USFWS 2011, p. I-8). A designation of critical habitat is intended to ameliorate habitat-based threats to an endangered or threatened species; critical habitat cannot reasonably be expected to address other, non-habitat-related threats to the species. In the case of the northern spotted owl, the recovery goal of supporting population viability and demographically stable populations of northern spotted owls will likely require habitat conservation in concert with the implementation of recovery actions that address other, non-habitat-based threats to the species, including the barred owl. In addition, recovery actions include scientific evaluation of potential management options to reduce the impact of barred owls on northern spotted owls (USFWS 2011, Recovery Action 29 [RA29], p. III-65), and implementation of management actions determined to be effective (USFWS 2011, Recovery Action 30 [RA30], p. III-65).

When developing a critical habitat rule, the Service must use the best scientific information available to identify those specific areas within the geographical area occupied by the species at the time it was listed that provide the physical and biological features essential for the conservation of the species, and that may require special management considerations or protection, or to identify those areas outside the geographical area occupied by the species at the time it was listed that are otherwise determined to be essential to the conservation of the species. However, like most critical habitat proposals, this rule addresses elements of risk management, because we must make recommendations and decisions in the face of incomplete information and uncertainty about factors influencing northern spotted owl populations. This uncertainty exists even though the northern spotted owl is among the most thoroughly studied of listed species. We understand a great deal about the habitats the subspecies prefers and the factors that influence its demographic trends. Nonetheless, considerable uncertainty remains, particularly about interactions among different factors that threaten the owl.

In the face of such uncertainty, the Revised Recovery Plan proposes strategies to address the primary threats to the northern spotted owl from habitat loss and barred owls (USFWS 2011, p. I-7) . The effects of climate change and of past management practices are changing forest ecosystem processes and dynamics, including patterns of wildfires, insect outbreaks and disease, to a degree greater than anticipated in the Northwest Forest Plan (NWFP) (Hessburg et al. 2005, pp. 134-135; Carroll et al. 2010, p. 899; Spies et al. 2010, entire; USFWS 2011, p. I-8). At the same time, the expansion of barred owl populations is altering the capacity of intact habitat to support northern spotted owls. Projecting the effects of these factors and their interactions into the future leads to even higher levels of uncertainty, especially considering how the influences of different threats may vary across the owl's large geographical range. It is clear that ecosystem-level changes are occurring within the northern spotted owl's forest habitat.

The development of a critical habitat network for the northern spotted owl must take into account the current uncertainty associated with both barred owl impacts and climate change predictions (USFWS 2011, p. III-10) as well as the uncertainty associated with how land will be managed in the future, how climate change effects will impact northern spotted owls, and whether and how barred owls will be managed (and thus, what the future effect of barred owls will be on northern spotted owl populations). These uncertainties require that we make some assumptions about likely future conditions in developing, modeling, and evaluating potential critical habitat for the northern spotted owl; those assumptions are identified clearly in this proposed rule (see Criteria Used to Identify Critical Habitat, below) and in our supporting documentation (Dunk et al. 2012, entire).

Given the continued decline of northern spotted owl populations, the apparent increase in severity of the threat from barred owls, and information indicating a recent loss of genetic diversity for the subspecies, retaining both occupied northern spotted owl sites and unoccupied, high-value northern spotted owl habitat across the subspecies' range are key components for recovery (USFWS 2011, p. I-9). Accordingly, in this proposed rule, we have identified areas of occupied habitat that provide the physical or biological features essential to the conservation of the northern spotted owl, and which may require special management considerations or protection. When occupied areas were not adequate to achieve recovery goals, we also identified some unoccupied areas as critical habitat for the northern spotted owl when it was clear that such areas are essential to the conservation of the species. However, it is important to note that this proposed revised designation of critical habitat does not include all sites where northern spotted owls are known to occur. The habitat modeling that we used, in part, to assist us in developing this proposed revised designation was based primarily on present habitat suitability. While we did also consider the present known locations of northern spotted owls in refining the identified habitat network, not all such sites were included in the proposed revised designation if those areas did not make a significant contribution to population viability (for example, if known sites were too small or isolated to play a meaningful role in the conservation of the species; see Criteria Used to Identify Critical Habitat). This is in accordance with Section 3(5)(C) of the Act, which specifies that “critical habitat shall not include the entire geographical area which can be occupied by the threatened or endangered species.”

Because of the uncertainties associated with the effects of barred owl interactions with the northern spotted owl and habitat changes that may occur as a result of climate change, active adaptive management strategies will be needed to achieve results in certain landscapes. Adaptive management is a systematic approach for improving resource management by learning from the results of explicit management policies and practices and applying that learning to future management decisions (USFWS 2011, p. G-1). This critical habitat rule identifies key sources of uncertainty, and the need to learn from our management of forests that provide habitat for northern spotted owls. We propose a critical habitat network that was developed based on what we believe to be essential for the conservation of the northern spotted owl, including information on essential habitats, the current distribution of those habitats, and the best available scientific knowledge about northern spotted owl population dynamics, while acknowledging uncertainty about future conditions in Pacific Northwest forests.

Section 2 of the Act states, “The purposes of this Act are to provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved.” Although the conservation of the listed species is the specific objective of a critical habitat designation, the essential physical or biological features that serve as the basis of critical habitat are often essential components of the ecosystem upon which the species depends. In such cases, a fundamental goal of critical habitat management is not only to conserve the listed species, but also to conserve the ecosystem upon which that species depends. This is the case with the northern spotted owl.

An “ecosystem” is defined as a biological community of interacting organisms and their physical environment, or as the complex of a community of organisms and its environment functioning as an ecological unit (Krebs 1972, pp. 10-11; Ricklefs 1979, pp. 31-32, 869). These ecosystem interactions and functions are often referred to as ecological “relationships” or “processes.” Thus, to conserve the northern spotted owl as directed by the Act, one must also conserve the ecological processes that occur within the ecological landscape inhabited by the species. These processes—such as vegetation succession, forest fire regimes, and nutrient cycling—create and shape the physical and biological features that form the foundation of critical habitat. The northern spotted owl was initially listed as a threatened species largely due to the loss or degradation of the late-successional forest ecosystems upon which it depends. A complex interaction of physical and biological factors contribute to the development and maintenance of these ecosystems, which in turn provide the northern spotted owl with the environmental conditions required for its conservation and survival, such as large areas of suitable habitat, nest structures, and sufficient prey to sustain interconnected populations of owls across the landscape. A fundamental goal of critical habitat management should thus be to understand, describe, and conserve these processes, which in turn will maintain the physical and biological features essential to the conservation of the species. This “ecosystem approach” will ultimately have the highest likelihood of conserving listed species such as the northern spotted owl in the long term (Knight 1998, p. 43).

Service policy also endorses this approach: “Species will be conserved best not by a species-by-species approach but by an ecosystem conservation strategy that transcends individual species” (59 FR 34724, July 1, 1994). The Service applies this ecosystem approach to critical habitat designations for other listed species (e.g., in Hawaii (75 FR 18960, April 13, 2010; 76 FR 46362, August 2, 2011)). Likewise, the U.S. Forest Service, which manages the great majority of the proposed northern spotted owl critical habitat, has prioritized restoring and maintaining natural ecological function and resiliency to its forest lands (Blate et al. 2009, entire; USDA 2010, entire; Tidwell 2011, entire). Active management of critical habitat is intended to be fully compatible and consistent with these landscape-level ecosystem conservation efforts.

Proposed revised critical habitat for the northern spotted owl includes a diverse forest landscape that covers millions of acres and contains several different forest ecosystems and thousands of plant and animal species. It ranges from dry, fire-prone forests to moist old-growth conifer forest to a mix of conifers and hardwood trees. Thousands of species occur in these forest ecosystems, including other listed species with very specific biological needs. Prescribed management for all of these needs at the species level on large landscapes is likely to be expensive, logistically difficult, and often in conflict (Thompson et al. 2009, p. 29). Many scientists believe a single-species approach to forest management is limited and that land managers need to focus on broader landscape goals that address ecosystem process and future habitat conditions (see, e.g., Thomas et al. 2006, p. 286; Boyd et al. 2008, p. 42; Hobbs et al. 2010, p. 487; Mori 2011, pp. 289-290). In this proposed revised designation of critical habitat, we encourage the application of ecosystem management principles to ensure the long-term conservation of the northern spotted owl and its habitat, as well as other species dependent on these shared ecosystems.

Another important development informing spotted owl critical habitat management involves changes in forestry science. Emulating natural disturbance regimes is emerging as a dominant paradigm in North American forest management (Seymour and Hunter 1999, p. 56; Long 2009, p. 1868). This change is occurring in response to: (1) The simplification of forests in terms of structure, age-class diversity, and species composition as a result of management for timber production, and (2) a recognition of fundamental changes in ecosystem function and processes due to land management practices, especially fire and successional patterns (Franklin et al. 2002, pp. 402-408; Hessburg et al. 2005, pp. 134-135; Drever et al. 2006, p. 2291). Although human disturbance is unlikely to precisely mimic natural forest disturbance, it can be used to better maintain the resilience of landscapes and wildlife populations to respond to natural disturbance and climate change (Lindenmayer et al. 2008, p. 87). In general, silviculture prescriptions that apply ecological forestry principles to address the conservation of broader ecological processes are compatible with maintaining the proposed critical habitat's essential features in the long term (USFWS 2011, p. III-14).

Explicitly prescribing such management at a fine scale (e.g., forest stand level) is beyond the scope of this document and should be developed at the appropriate land management unit (e.g., National Forest or BLM District; USDA 2010, entire) and through consultation with the Service, as appropriate. As described below and in the Revised Recovery Plan, management actions whose intent is to conserve or restore natural ecological processes and enhance forest resilience in the long term should generally be consistent with the goals of critical habitat management (USFWS 2011, p. III 11-39). The Service has recently approved these types of management actions in occupied spotted owl habitat on BLM and USFS lands.

Some general considerations for managing within spotted owl critical habitat are discussed in more detail in the Special Management Considerations and Adverse Modification sections of this document. In sum, vegetation and fuels management in dry and mixed-dry forests is encouraged both within and outside designated critical habitat where the goal of such treatment is to conserve natural ecological processes or restore them (including fire) where they have been modified or suppressed (Allen et al. 2002, pp. 1429-1430; Spies et al. 2006, pp. 358-361; Fielder et al. 2007, entire; Prather et al. 2008, entire; Lindenmayer et al. 2009, p. 274; Tidwell 2011, entire). Likewise, in moist and some mixed forests, management of spotted owl critical habitat should be compatible with broader ecological goals, such as the retention of high-quality older forest, the continued treatment of young or homogenous forest plantations, and the conservation or restoration of complex early seral forest habitat (Spies et al. 2007b, pp. 57-63; Betts et al. 2010, pp. 2117, 2126-2127; Swanson at al. 2010, entire). In general, actions that promote ecological restoration and those that apply ecological forestry principles as described in the Revised Recovery Plan (USFWS 2011, pp. III-11 to III-41) are likely to be consistent with the conservation of the northern spotted owl and the management of its critical habitat.

It is important for readers of this document to understand the relationship between spotted owl critical habitat and the Northwest Forest Plan (NWFP). Critical habitat for the spotted owl was first designated in 1992 (January 15, 1992; 57 FR 1796). Since 1994, the NWFP has also served as an important landscape-level plan that has contributed to the conservation of the northern spotted owl and its late-successional forest habitat (Thomas et al. 2006, pp. 278-284). The NWFP introduced a strategy of reserves where conservation would be the priority, and matrix areas where timber harvest would be the goal. Here we briefly provide a summary of how our proposed designation of critical habitat has been informed by the knowledge and experience gained from management under the NWFP.

The NWFP reserve strategy has been successful in the conservation and recruitment of late-successional forest and associated species on Federal lands (Thomas et al. 2006, p. 283). Implementation of the plan has been less successful in providing the anticipated level of commercial timber harvest from matrix lands (less than 50 percent of anticipated levels; Thomas et al. 2006, p. 284), at promoting active restoration in areas that may contain uncharacteristically high risk of severe fire (Spies et al. 2006, pg. 359; Thomas et al. 2006, p. 277), or in moist forests where early seral habitats are lacking such as those described above (Betts et al. 2010, p. 2117).

Some scientists have suggested that it may be time to reconsider various recommendations or requirements of the NWFP in light of improved scientific insight, increasing concerns over future ecological conditions that appear increasingly dynamic, and changing social values (Spies et al. 2006, p. 360; Thomas et al. 2006, p. 286; Thompson et al. 2009, p. 29). Some specifically question the strategy of managing Federal lands in the range of the northern spotted owl separately as reserves in some areas and for commodity production in others, suggesting a more holistic management perspective (Spies et al. 2006, p. 360; Thomas et al. 2006, p. 286; Franklin and Lindenmayer 2009, entire). Other scientists conclude that a system of large reserves in the NWFP is still necessary for course-scale planning, but that fine-scale management should proceed that restores ecological processes while minimizing adverse impacts to wildlife (Carroll et al. 2009, p. 29).

The Service, in developing this proposed critical habitat designation, has taken these concerns into consideration. Thomas et al. (2006, pp. 284-287) recommend three primary improvements in the NWFP to address these concerns. These recommendations are highly relevant to spotted owl critical habitat management:

1. Conserve old growth trees and forests on Federal lands wherever they are found (emphasis added), and undertake appropriate restoration treatment in the threatened forest types.

2. Manage NWFP forests as dynamic ecosystems that conserve all stages of forest development (e.g., old growth and early seral), and where tradeoffs between short-term and long-term risks are better balanced.

3. Recognize the NWFP as an integrated conservation strategy that contributes to all components of sustainability across Federal lands.

The management of critical habitat for the spotted owl should be compatible with these broader landscape management goals articulated by Thomas et al. (2006, pp. 284-287). Critical habitat for the northern spotted owl is not intended to be a “hands off” reserve in the traditional sense. Rather, it should be a “hands-on” ecosystem management landscape that should include a mix of active and passive actions to meet a variety of conservation goals that support long-term spotted owl conservation. Some general considerations for managing for the conservation of the northern spotted owl are discussed in the Special Management Considerations and Adverse Modification sections of this document, as well as in the Revised Recovery Plan for the Northern Spotted Owl (USFWS 2011, pp. III-11 to III-39).

The northern spotted owl is a medium-sized owl and the largest of the three subspecies of spotted owls currently recognized by the American Ornithologists' Union (Gutiérrez et al. 1995, p. 2). It is dark brown with a barred tail and white spots on the head and breast, and has dark brown eyes that are surrounded by prominent facial disks. The taxonomic separation of these three subspecies is supported by numerous factors (reviewed in Courtney et al. 2004, pp. 3-3 to 3-31), including genetic (Barrowclough and Gutiérrez 1990, p. 739; Barrowclough et al. 1999, p. 922; Haig et al. 2004, p. 1353; Barrowclough et al. 2005, p. 1113), morphological (Gutiérrez et al. 1995, pp. 2 to 3), behavioral (Van Gelder 2003, p. 30), and biogeographical characteristics (Barrowclough et al. 1999, p. 928).

The current range of the northern spotted owl extends from southwest British Columbia through the Cascade Mountains, coastal ranges, and intervening forested lands in Washington, Oregon, and California, as far south as Marin County, California. The subspecies is listed as threatened under the Act throughout its range (55 FR 26114; June 26, 1990). Within the United States, the northern spotted owl ranges across 12 physiographic provinces, based on recognized landscape subdivisions exhibiting different physical and environmental features, often referred to as “physiographic provinces” (Franklin and Dyrness 1988, pp. 5-26; Thomas et al. 1990, p. 61; USDA and USDI 1994, p. A-3). These include the Olympic Peninsula, Western Washington Lowlands, Western Washington Cascades, Eastern Washington Cascades, Oregon Coast Ranges, Western Oregon Cascades, Willamette Valley, Eastern Oregon Cascades, Oregon Klamath, California Klamath, California Coast Ranges, and California Cascades Provinces (based on USDA and USDI 1994, p. A-3). Very few northern spotted owls are found in British Columbia, the Western Washington Lowlands or Willamette Valley; therefore, the subspecies is restricted primarily to 10 of the 12 provinces within its range.

For the purposes of developing this proposed rule, and based on Appendix C of the Revised Recovery Plan (USFWS 2011, pp. C-7 to C-13), we have divided the range of the northern spotted owl into 11 different regions. We used these 11 regions in the habitat modeling that informed this proposed revised designation of critical habitat. The regions used here are more “owl specific” than the physiographic provinces used in the past. In addition to regional patterns of climate, topography, and forest communities, which the physiographic provinces also considered, the 11 regions are additionally based on specific patterns of spotted owl habitat relationships and prey base relationships across the range of the species. A map of the 11 regions used for the purposes of habitat modeling is provided in the Revised Recovery Plan (USFWS 2011, p. C-13), and are also shown in Figure 1 of this document. We additionally used these 11 regions identified in the Revised Recovery Plan as the organizing units for our designation of critical habitat.

Spotted owls generally rely on older forested habitats because such forests contain the structures and characteristics required for nesting, roosting, and foraging, and dispersal. Forest characteristics associated with spotted owls usually develop with increasing forest age, but their occurrence may vary by location, past forest practices, and stand type, history, and condition. Although spotted owl habitat is variable over its range, some general attributes are common to the owl's life-history requirements throughout its range. To support northern spotted owl reproduction, a home range requires appropriate amounts of nesting, roosting, and foraging habitat arrayed so that nesting pairs can survive, obtain resources, and breed successfully. In northern parts of the range where nesting, roosting, and foraging habitat have similar attributes, nesting is generally associated with increasing old forest in the core area (Swindle et al. 1999, p. 1216). In some southern portions of the range, northern spotted owl survival is positively associated with the area of old forest habitat in the core, but reproductive output is positively associated with amount of edge between older forest and other habitat types in the home range (Franklin et al. 2000, pp. 573, 579). This pattern suggests that where dusky-footed woodrats ( Neotoma fuscipes ) are the primary prey species, core areas that have nesting habitat stands interspersed with varied types of foraging habitat may be optimal for northern spotted owl survival and reproduction. Both the amount and spatial distribution of nesting, roosting, foraging, and dispersal habitat influence reproductive success and long-term population viability of northern spotted owls.

Population growth can occur only if there is adequate habitat in an appropriate configuration to allow for the dispersal of owls across the landscape. This includes support of dispersing juveniles, as well as nonresident subadults and adults that have not yet recruited into the breeding population. The survivorship of northern spotted owls is likely greatest when dispersal habitat most closely resembles nesting, roosting, and foraging habitat, but owls may use other types of habitat for dispersal on a short-term basis. Dispersal habitat, at a minimum, consists of stands with adequate tree size and canopy closure to provide protection from avian predators and at least minimal foraging opportunities (57 FR 1805, January 15, 1992).

The three essential functions served by habitat within the home range of a northern spotted owl are:

(1) Nesting. Nesting habitat is essential to provide structural features for nesting, protection from adverse weather conditions, and cover to reduce predation risks. Habitat requirements for nesting and roosting are nearly identical. However, nesting habitat is specifically associated with a high incidence of large trees with various deformities (large cavities, broken tops, mistletoe ( Arceuthobium spp.) infections, and other evidence of decadence) or large snags suitable for nest placement. Additional features that support nesting and roosting typically include a moderate to high canopy closure; a multilayered, multi-species canopy with large overstory trees; large accumulations of fallen trees and other woody debris on the ground; and sufficient open space below the canopy for spotted owls to fly (Thomas et al. 1990, p. 164). Forested stands with high canopy closure also provide thermal cover (Weathers et al. 2001, p. 686) and protection from predators. Patches of nesting habitat, in combination with roosting habitat, must be sufficiently large and contiguous to maintain northern spotted owl core areas and home ranges, and must be proximate to foraging habitat. Ideally, nesting habitat also functions as roosting, foraging, and dispersal habitat.

(2) Roosting. Roosting habitat is essential to provide for thermoregulation, shelter, and cover to reduce predation risk while resting or foraging. As noted above, the same habitat generally serves for both nesting and roosting functions; technically “roosting habitat” differs from nesting habitat only in that it need not contain those specific structural features used for nesting (cavities, broken tops, and mistletoe platforms), but does contain moderate to high canopy closure; a multi-layered, multi-species canopy; large accumulations of fallen trees and other woody debris on the ground; and open space below the canopy for northern spotted owls to fly. In practice, however, roosting habitat is not segregated from nesting habitat. Nesting and roosting habitat will also function as foraging and dispersal habitat.

(3) Foraging. Foraging habitat is essential to provide a food supply for survival and reproduction. Foraging habitat is the most variable of all habitats used by territorial spotted owls, and is closely tied to the prey base, as described below. Nesting and roosting habitat always provides for foraging, but in some cases owls also use more open and fragmented forests, especially in the southern portion of the range where some younger stands may have high prey abundance and structural attributes similar to those of older forests, such as moderate tree density, subcanopy perches at multiple levels, multi-layered vegetation, or residual older trees. Foraging habitat generally has attributes similar to those of nesting and roosting habitat, but foraging habitat may not always support successfully nesting pairs (USDI 1992, pp. 22-25). Foraging habitat can also function as dispersal habitat. The primary function of foraging habitat is to provide a food supply for survival and reproduction.

Because northern spotted owls show a clear geographical pattern in diet, and different prey species prefer different habitat types, prey distribution contributes to differences in northern spotted owl foraging habitat selection across the range. In the northern portion of their range, northern spotted owls forage heavily in older forests or forests with similar complex structure that support northern flying squirrels ( Glaucomys sabrinus ) Carey et al. 1992, p. 233; Rosenberg and Anthony 1992, p. 165). In the southern portion of their range, where woodrats are a major component of their diet, northern spotted owls are more likely to use a variety of stands, including younger stands, brushy openings in older stands, and edges between forest types in response to higher prey density in some of these areas (Solis 1983, pp. 89-90; Sakai and Noon 1993, pp. 376-378; Sakai and Noon 1997, p. 347; Carey et al. 1999, p. 73; Franklin et al. 2000, p. 579). Both the amount and distribution of foraging habitat within the home range influence the survival and reproduction of northern spotted owls.

Successful dispersal of northern spotted owls is essential to maintaining genetic and demographic connections among populations across the range of the species. Habitats that support movements between larger habitat patches that provide nesting, roosting, and foraging habitats for northern spotted owls act to limit the adverse genetic effects of inbreeding and genetic drift and provide demographic support to declining populations (Thomas et al. 1990, pp. 271-272). Dispersing juvenile northern spotted owls experience high mortality rates (more than 70 percent in some studies (Miller 1989, pp. 32-41; Franklin et al. 1999, pp. 25, 28; 55 FR 26115; June 26, 1990)) from starvation, predation, and accidents (Miller 1989, pp. 41-44; Forsman et al. 2002, pp. 18-19). Juvenile dispersal is thus a highly vulnerable life stage for northern spotted owls, and enhancing the survivorship of juveniles during this period could play an important role in maintaining stable populations of northern spotted owls.

Successful juvenile dispersal may depend on locating unoccupied suitable habitat in close proximity to other occupied sites (LaHaye et al. 2001, pp. 697-698). Dispersing juveniles are likely attracted to conspecific calls, and may look for suitable sites preferentially in the vicinity of occupied territories. When all suitable territories are occupied, dispersers may temporarily pursue a nonresident (nonbreeding) strategy; such individuals are sometimes referred to as “floaters” (Forsman et al. 2002, pp. 15, 26). Floaters prospect for territorial vacancies created when residents die or leave their territories. Floaters contribute to stable or increasing populations of northern spotted owls by quickly filling territorial vacancies. Where large blocks of habitat with multiple breeding pairs occur, the opportunities for successful recruitment of dispersers and floaters are enhanced due to the within-block production of potential replacement birds (Thomas et al. 1990, pp. 295, 307).

Juvenile dispersal occurs in steps (Forsman et al. 2002, pp. 13-14), between which dispersing juveniles settle into temporary home ranges for up to several months (Forsman et al. 2002, p. 13). Natal dispersal distances, measured from natal areas to eventual home range, tend to be larger for females (about 15 mi (24 km)) than males (about 8.5 mi (13.7 km)) (Courtney et al. 2004, p. 8-5). Forsman et al. (2002, pp. 15-16) reported dispersal distances of 1,475 spotted owls in Oregon and Washington for the period from 1985 to 1996. Median maximum dispersal distance (the straight-line distance between the natal site and the farthest location) for radio-marked juvenile male spotted owls was 12.7 mi (20.3 km), and that of female spotted owls was 17.2 mi (27.5 km) (Forsman et al. 2002, Table 2).

Spotted owls can utilize forests with the characteristics of nesting, roosting, or foraging for dispersal, and likely experience greater survivorship under such conditions. However, dispersing or nonresident individuals may also make use of other forested areas that do not meet the requirements of nesting or roosting habitat on a short-term basis. Such short-term dispersal habitats must, at minimum, consist of stands with adequate tree size and canopy closure to provide protection from avian predators and at least minimal foraging opportunities.

Demographic data from studies initiated as early as 1985 have been analyzed every 5 years to estimate northern spotted owl demographic rates and population trends (Anderson and Burnham 1992, entire; Burnham et al. 1994, entire; Franklin et al. 1999, entire; Anthony et al. 2006, entire; Forsman et al. 2011, entire). The most current evaluation of population status and trends is based on data through 2008 (Forsman et al. 2011, p. 1). Based on this analysis, populations on 7 of 11 study areas (Cle Elum, Rainier, Olympic Peninsula, Oregon Coast Ranges, H.J. Andrews, Northwest California, and Green Diamond) were declining (Forsman et al. 2011, p. 64, Table 22).

Estimates of realized population change (cumulative population change across all study years) indicated that, in the more rapidly declining populations (Cle Elum, Rainier, and Olympic Peninsula), the 2006 populations were 40 to 60 percent of the population sizes observed in 1994 or 1995 (Forsman et al. 2011, pp. 47-49). Populations at the remaining areas (Tyee, Klamath, Southern Oregon Cascades, and Hoopa) showed declining population growth rates as well, although the estimated rates were not significantly different from stable populations (Forsman et al. 2011, p 64). A meta-analysis combining data from all 11 study areas indicates that rangewide the population declined at a rate of about 2.9 percent per year for the period from 1985 to 2006. Northern spotted owl populations on Federal lands had better demographic rates than elsewhere, but still declined at a mean annual rate of about 2.8 percent per year for 1985-2006 (Forsman et al. 2011, p. 67).

In addition to declines in population growth rates, declines in annual survival were reported for 10 of the 11 study areas (Forsman et al. 2011, p. 64, Table 22). Number of young produced each year showed declines at 5 areas (Cle Elum, Klamath, Southern Oregon Cascades, Northwest California, and Green Diamond), was relatively stable at 3 areas (Olympic Peninsula, Tyee, Hoopa), and was increasing at 2 areas (Oregon Coast Ranges, H. J. Andrews) (Forsman et al. 2011, p. 64 Table 22).

As noted above, the barred owl has emerged as a greater threat to the northern spotted owl than was previously recognized. The range of the barred owl has expanded in recent years and now completely overlaps that of the northern spotted owl (Crozier et al. 2006, p. 761). The presence of barred owls has significant negative effects on northern spotted owl reproduction (Olson et al. 2004, p. 1048), survival (Anthony et al 2006, p. 32), and number of territories occupied (Kelly et al. 2003, p. 51; Olson et al. 2005, p. 928). The determination of population trends for the northern spotted owl has become complicated by the finding that northern spotted owls are less likely to call when barred owls are also present; therefore, they are more likely to be undetected by standard survey methods (Olson et al. 2005, pp. 919-929; Crozier et al. 2006, pp. 766-767). As a result, it is difficult to determine whether northern spotted owls no longer occupy a site, or whether they may still be present but are not detected. The 2011 Revised Recovery Plan for the Northern Spotted Owl concludes that “barred owls are contributing to the population decline of spotted owls, especially in Washington, portions of Oregon, and the northern coast of California.” (USFWS 2011, p. B-12).

British Columbia has a small population of northern spotted owls. This population has declined at least 49 percent since 1992 (Courtney et al. 2004, p. 8-14), and by as much as 90 percent since European settlement (Chutter et al. 2004, p. 6) to a 2004 breeding population estimated at about 23 birds (Sierra Legal Defence [sic] Fund and Western Canada Wilderness Committee 2005, p. 16) on 15 sites (Chutter et al. 2004, p. 26). Chutter et al. (2004, p. 30) suggested immediate action was required to improve the likelihood of recovering the spotted owl population in British Columbia. In 2007, the Spotted Owl Population Enhancement Team recommended to remove spotted owls from the wild in British Columbia. Personnel in British Columbia captured and brought into captivity the remaining 16 known wild spotted owls. Prior to initiating the captive-breeding program, the population of spotted owls in Canada was declining by as much as 35 percent per year (Chutter et al. 2004, p. 6). The amount of previous interaction between northern spotted owls in Canada and the United States is unknown (Chutter et al. 2004, p. 24). Although the status of the spotted owl in Canada is informative in terms of the overall declining trend of the northern spotted owl throughout its range, and consequently the increased need for conservation in those areas where it persists, the Service does not designate critical habitat in foreign countries (50 CFR 424.12(h)).

Northern spotted owls are a long-lived species with relatively stable and high rates of adult survival, lower rates of juvenile survival, and highly variable reproduction. Franklin et al. (2000, p. 576) suggested that northern spotted owls follow a “bet-hedging” life-history strategy, where natural selection favors individuals that reproduce only during favorable conditions. For such species, population growth rate is more susceptible to changes in adult survival than to recruitment of new individuals into the population. For northern spotted owls, recent demographic analyses have indicated declining trends in both adult survival and recruitment across much of the species range (Forsman et al. 2011, p. 64, Table 22).

Northern spotted owls are highly territorial (Courtney et al. 2004, p. 2-7), though overlap between the outer portions of the home ranges of adjacent pairs is common (Forsman et al. 1984, pp. 5, 17, 22-24; Solis and Gutiérrez 1990, p. 742; Forsman et al. 2005, p. 374). Pairs are nonmigratory and remain on their home range throughout the year, although they often increase the area used for foraging during fall and winter (Forsman et al. 1984, p. 21; Sisco 1990, p. 9), likely in response to potential depletion of prey in the core of their home range (Carey et al. 1992, p. 245; Carey 1995, p. 649; but see Rosenberg et al. 1994, entire). The northern spotted owl shows strong year-round fidelity to its territory, even when not nesting (Solis 1983, pp. 23-28; Forsman et al. 1984, pp. 52-53) or after natural disturbance alters habitat characteristics within the home range (Bond et al. 2002, pp. 1024-1026). A discussion of northern spotted owl home range size and use is included in the Primary Constituent Elements section of this proposed rule.

Reproductive success of northern spotted owls has been characterized as a multi-stage process in which natal dispersal and survival to reproductive age are the most vulnerable stages (Carey and Peeler 1995, p. 236). Nomadic adults and juveniles dispersing from their natal area serve as sources of replacements for resident northern spotted owls that die or leave their home range (Thomas et al. 1990, p. 295). Habitat supporting movements of northern spotted owls between large habitat blocks is essential for successful dispersal of both juvenile and adult owls (Thomas et al. 1990, p. 271). The ability of individuals to move among more isolated populations reduces potentially adverse genetic effects of inbreeding and provides demographic support to declining populations (Thomas et al. 1990, pp. 271-272). A discussion of northern spotted owl dispersal is included in the Physical and Biological Features and Primary Constituent Elements sections of this proposed rule.

Northern spotted owl diets vary across owl territories, years, seasons, and geographical regions (Forsman et al. 2001, pp.146-148; 2004, pp. 217-220). However, four to six species of nocturnal mammals typically dominate their diets (Forsman et al. 2004, p. 218), with northern flying squirrels being a primary prey species in all areas. In Washington, diets are dominated by northern flying squirrels, snowshoe hare ( Lepus americanus ), bushy-tailed woodrats ( Neotoma cinerea ), and boreal red-backed voles ( Clethrionomys gapperi ) (Forsman et al. 2001, p. 144). In Oregon and northern California, northern flying squirrels in combination with dusky-footed woodrats, bushy-tailed woodrats, red tree voles ( Arborimus longicaudus ), and deer mice ( Peromyscus maniculatus ) comprise the majority of diets (Courtney et al. 2004, pp. 41-31 to 4-32; Forsman et al. 2004, p. 221). Northern spotted owls are also known to prey on insects, other terrestrial mammals, birds, and juveniles of larger mammals (e.g., mountain beaver ( Aplodontia rufa ) (Forsman et al. 2001, p. 146; 2004, p. 223).

Northern flying squirrels are positively associated with late-successional forests with high densities of large trees and snags (Holloway and Smith 2011, p. 671). Northern flying squirrels typically use cavities in large snags as den and natal sites, but may also use cavities in live trees, hollow branches of fallen trees, crevices in large stumps, stick nests of other species, and lichen and twig nests they construct (Carey 1995, p. 658). Fungi (mychorrhizal and epigeous types) are prominent in their diet; however, seeds, fruits, nuts, vegetation matter, insects, and lichens may also represent a significant proportion of their diet (summarized in Courtney et al. 2004, App. 4 p. 3-12). Northern flying squirrel densities tend to be higher in older forest stands with ericaceous shrubs (e.g., Pacific rhododendron ( Rhododendron macrophyllum )) and an abundance of large snags (Carey 1995, p. 654), likely because these older forests produce a higher forage biomass. Flying squirrel density tends to increase with stand age (Carey 1995, pp. 653-654; Carey 2000, p. 252), although managed and second-growth stands sometimes also show high densities of squirrels, especially when canopy cover is high (e.g., Rosenberg and Anthony 1992, p. 163; Lehmkuhl et al. 2006, pp. 589-591). The main factors that may limit northern flying squirrel densities are the availability of den structures and food, especially hypogeous (below ground) fungi or truffles (Gomez et al. 2005, pp. 1677-1678).

For northern spotted owls in Oregon, both dusky-footed and bushy-tailed woodrats are important prey items (Forsman et al. 2004, pp. 226-227), whereas in Washington owls rely primarily on the bushy-tailed woodrat (Forsman et al. 2001, p. 144). Habitats that support bushy-tailed woodrats usually include early seral mixed-conifer/mixed-evergreen forests close to water (Carey et al. 1999, p. 77). Bushy-tailed woodrats reach high densities in both old forests with openings and closed-canopy young forests (Sakai and Noon 1993, pp. 376-378; Carey et al. 1999, p. 73), and use hardwood stands in mixed-evergreen forests (Carey et al. 1999, p. 73). Bushy-tailed woodrats are important prey species south of the Columbia River and may be more limited by abiotic features, such as the availability of suitable rocky areas for den sites (Smith 1997, p. 4) or the presence of streams (Carey et al. 1992, p. 234; 1999, p. 72). Dense woodrat populations in shrubby areas are likely a source of colonists to surrounding forested areas (Sakai and Noon 1997, p. 347), therefore forested areas with nearby open, shrubby vegetation generally support high numbers of woodrats. The main factors that may limit woodrats are access to stable, brushy environments that provide food, cover from predation, materials for nest construction, dispersal ability, and appropriate climatic conditions (Carey et al. 1999, p. 78).

Territorial northern spotted owls remain resident on their home range throughout the year; therefore, these homes ranges must provide all the habitat components needed for the survival and successful reproduction of a pair of owls. Northern spotted owls exhibit central-place foraging behavior (Rosenberg and McKelvey 1999, p. 1036), with much activity centered within a core area surrounding the nest tree during the breeding season. During fall and winter as well as in nonbreeding years, owls often roost and forage in areas of their home range more distant from the core. In nearly all studies of northern spotted owl habitat use, the amount of mature and old-growth forest was greater in core areas and home ranges than at random sites on the landscape (Courtney et al. 2004, pp. 5-6, 5-13; also see USFWS 2011, Appendix G for definitions of mature and old-growth forest), and forests were less fragmented within spotted owl home ranges (Hunter et al. 1995, p. 688). The amount of habitat at the core area scale shows the strongest relationships with home range occupancy (Meyer et al. 1998, p. 34; Zabel et al. 2003, p. 1036), survival (Franklin et al. 2000, p. 567; Dugger et al. 2005, p. 873), and reproductive success (Ripple et al. 1997, pp. 155-156; Dugger et al. 2005, p. 871). A more complete description of the home range is presented in the Physical or Biological Features section of this document, under “Population Spatial Requirements.”

The size, configuration, and characteristics of vegetation patches within home ranges affect northern spotted owl survival and reproduction, a concept referred to as habitat fitness potential (Franklin et al. 2000, p. 542). Among studies that have estimated habitat fitness potential, the effects of forest fragmentation and heterogeneity vary geographically. In the California Klamath Province, locations for nesting and roosting tend to be centered in larger patches of old forest, but edges between forest types may provide increased prey abundance and availability (Franklin et al. 2000, p. 579). In the central Oregon Coast Range, northern spotted owls appear to benefit from a mixture of older forests with younger forest and nonforested areas in their home range (Olson et al. 2004, pp. 1049-1050), a pattern similar to that found in the California Klamath Province. Courtney et al. (2004, p. 5-23) suggest that although in general large patches of older forest appear to be necessary to maintain stable populations of northern spotted owls, home ranges composed predominantly of old forest may not be optimal for northern spotted owls in the California Klamath Province and Oregon Coast Ranges Province.

The northern spotted owl inhabits most of the major types of coniferous forests across its geographical range, including Sitka spruce ( Picea sitchensis ), western hemlock ( Tsuga heterophylla ), mixed conifer and mixed evergreen, grand fir ( Abies grandis ), Pacific silver fir ( A. amabilis ), Douglas-fir ( Pseudotsuga menziesii ), redwood ( Sequoia sempervirens )/Douglas-fir (in coastal California and southwestern Oregon), white fir ( A. concolor ), Shasta red fir ( A.magnifica var. shastensis ), and the moist end of the ponderosa pine ( Pinus ponderosa ) zone (Forsman et al. 1984, pp. 15-16; Thomas et al. 1990, p. 145). Habitat for northern spotted owls has traditionally been described as consisting of four functional types: Nesting, roosting, foraging, and dispersal habitats. Recent studies continue to support the practical value of discussing northern spotted owl habitat usage by classifying it into these functional habitat types (Irwin et al. 2000, p. 183; Zabel et al. 2003, p. 1028; Buchanan 2004, p. 1334; Davis and Lint 2005, p. 21; Forsman et al. 2005, p. 372), and data from studies are available to describe areas used for these types of activities, so we retain it here to structure our discussion of the physical or biological features of habitat essential to the conservation of the northern spotted owl.

Recent habitat modeling efforts have also accounted for differences in habitat associations across regions, which have often been attributed to regional differences in forest environments and factors including available prey species (USFWS 2011, p. C-7). These recent advances allowed for modeling of northern spotted owl habitat by regions to account for: (1) The degree of similarity between nesting/roosting and foraging habitats based on prey availability; (2) latitudinal patterns of topology and climate; (3) regional patterns of topography, climate, and forest communities; and (4) geographical distribution of habitat elements that influence the range of conditions occupied by northern spotted owls (USFWS 2011, p. C-8). Detailed characterizations of each of these functional habitat types and their relative distribution are described in the Physical or Biological Features and Primary Constituent Elements section of this document.

There is growing evidence that recent climate change has impacted a wide range of ecological systems (Stenseth et al. 2002, entire; Walther et al. 2002, entire; Adahl et al. 2006, entire; Karl et al. 2009, entire). Climate change, combined with effects from past management practices, is exacerbating changes in forest ecosystem processes and dynamics to a greater degree than originally anticipated under the NWFP. Environmental variation affects all wildlife populations; however, climate change presents new challenges as systems may change beyond historical ranges of variability. In some areas, changes in weather and climate may result in major shifts in vegetation communities that can persist in particular regions.

Climate change will present unique challenges to the future of northern spotted owl populations and their habitats. Northern spotted owl distributions (Carroll 2010, entire) and population dynamics (Franklin et al. 2000, entire; Glenn et al. 2010, entire; 2011a, entire; 2011b, entire) may be directly influenced by changes in temperature and precipitation. In addition, changes in forest composition and structure as well as prey species distributions and abundance resulting from climate change may impact availability of habitat across the historical range of the subspecies. The Revised Recovery Plan provides a detailed discussion of the possible environmental impacts to the habitat of the northern spotted owl from the projected effects of climate change (USFWS 2011, pp. III-5 to III-11).

Because both spotted owl population dynamics and forest conditions are likely to be influenced by large-scale changes in climate in the future, we have attempted to account for these influences in our designation of critical habitat by recognizing that forest composition may change beyond the range of historical variation and that climate changes may have unpredictable consequences for both Pacific Northwest forests and northern spotted owls. This proposed critical habitat designation recognizes that forest management practices that promote ecosystem health under changing climate conditions will be essential for spotted owl conservation.

The northern spotted owl was listed as a threatened species on June 26, 1990 (55 FR 26114); a description of the relevant previous Federal actions up to the time of listing can be found in that final rule. On January 15, 1992, we published a final rule designating 6,887,000 acres (ac) (2,787,000 hectares (ha)) of Federal lands in Washington, Oregon, and California as critical habitat for the northern spotted owl (57 FR 1796). On January 13, 2003, we entered into a settlement agreement with the American Forest Resources Council, Western Council of Industrial Workers, Swanson Group Inc., and Rough & Ready Lumber Company, to conduct a 5-year status review of the northern spotted owl and consider potential revisions to its critical habitat ( Western Council of Industrial Workers (WCIW) v. Secretary of the Interior, Civ. No. 02-6100-AA (D. Or.) ). On April 21, 2003, we published a notice initiating the 5-year review of the northern spotted owl (68 FR 19569), and published a second information request for the 5-year review on July 25, 2003 (68 FR 44093). We completed the 5-year review on November 15, 2004, concluding that the northern spotted owl should remain listed as a threatened species under the Act (USFWS 2004, entire). On November 24, 2010, we published a notice initiating a new 5-year review for the northern spotted owl (75 FR 71726); the information solicitation period for this review was reopened from April 20, 2011 through May 20, 2011 (76 FR 22139), and the completed review was signed on September 29, 2011, concluding that the northern spotted owl was appropriately listed as a threatened species.

In compliance with the settlement agreement, as amended in the WCIW case, we published a proposed revised critical habitat rule in the Federal Register on June 12, 2007 (72 FR 32450). On May 21, 2008, we published a notice announcing the availability of a draft economic analysis and the reopening of the public comment period on the proposed revised critical habitat designation (73 FR 29471). This notice also alerted the public of the opportunity to comment on the proposed revision of critical habitat in the context of the recently released Recovery Plan for the Northern Spotted Owl, which was released on May 16, 2008, and announced in the Federal Register on May 21, 2008 (73 FR 29471). The 2008 recovery plan formed the basis for the current designation of northern spotted owl critical habitat, which we published in the Federal Register on August 13, 2008 (73 FR 47325).

Both the 2008 critical habitat designation and the 2008 recovery plan were challenged in court ( Carpenters' Industrial Council v. Salazar, Case No. 1:08-cv-01409-EGS (D.DC)). In addition, on December 15, 2008, the Inspector General of the Department of the Interior issued a report entitled “Investigative Report of The Endangered Species Act and the Conflict between Science and Policy,” which concluded that the integrity of the agency decision-making process for the spotted owl recovery plan was potentially jeopardized by improper political influence. As a result, the Federal Government filed a motion in the lawsuit for remand of the 2008 recovery plan and the critical habitat designation that was based on it. On September 1, 2010, the Court issued an opinion remanding the 2008 recovery plan to us for issuance of a revised plan within 9 months. On September 15, 2010, we published a Federal Register notice (75 FR 56131) announcing the availability of the Draft Revised Recovery Plan for the Northern Spotted Owl, and opened a 60-day comment period through November 15, 2010. On November 12, 2010, we announced by way of press release an extension of the comment period until December 15, 2010.

On November 30, 2010, we announced in the Federal Register the reopening of the public comment period until December 15, 2010 (75 FR 74073). At that time we also announced the availability of a synopsis of the population response modeling results for public review and comment. The supporting information regarding the modeling process was posted on our Web site. Of the approximately 11,700 comments received on the Draft Revised Recovery Plan, many requested the opportunity to review and comment on more detailed information on the habitat modeling process in Appendix C. On April 22, 2011, we reopened the comment period on Appendix C of the draft revised recovery plan (76 FR 22720); this comment period closed on May 23, 2011. On May 6, 2011, the Court granted our request for an extension of the due date for issuance of the final revised recovery plan until July 1, 2011. We published the notice of availability of the final Revised Recovery Plan for the Northern Spotted Owl in the Federal Register on July 1, 2011 (76 FR 38575).

On October 12, 2010, the Court remanded the 2008 critical habitat designation, which had been based on the 2008 Recovery Plan for the Northern Spotted Owl, and adopted the Service's proposed schedule to issue a new proposed revised critical habitat rule for public comment by November 15, 2011, and a final rule by November 15, 2012. The Court has subsequently extended the date for delivery of the proposed rule to the Federal Register to February 28, 2012; the due date of November 15, 2012, for issuance of the final revised rule remains unchanged. This proposed revision of critical habitat for the northern spotted owl is in response to the Court's order.

Critical habitat is defined in section 3 of the Act as:

(1) The specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the Act, on which are found those physical or biological features;

(a) Essential to the conservation of the species; and

(b) Which may require special management considerations or protection; and

(2) Specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.

Conservation, as defined under section 3 of the Act, means to use and the use of all methods and procedures that are necessary to bring an endangered or threatened species to the point at which the measures provided pursuant to the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transplantation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking.

Critical habitat receives protection under section 7 of the Act through the requirement that Federal agencies ensure, in consultation with the Service, that any action they authorize, fund, or carry out is not likely to result in the destruction or adverse modification of critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation does not allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by non-Federal landowners. Where a landowner requests Federal agency funding or authorization for an action that may affect a listed species or critical habitat, the consultation requirements of section 7(a)(2) of the Act would apply, but even in the event of a destruction or adverse modification finding, the obligation of the Federal action agency and the landowner is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.

Under the first prong of the Act's definition of critical habitat, areas within the geographical area occupied by the species at the time it was listed are included in a critical habitat designation if they contain physical or biological features: (1) Which are essential to the conservation of the species, and (2) which may require special management considerations or protection. For these areas, critical habitat designations identify, to the extent known using the best scientific and commercial data available, those physical or biological features that are essential to the conservation of the species (such as space, food, cover, and protected habitat). In identifying those physical and biological features within an area, we focus on the principal biological or physical constituent elements (primary constituent elements such as roost sites, nesting grounds, rainfall, canopy cover, soil type) that are essential to the conservation of the species.

Under the second prong of the Act's definition of critical habitat, we can designate critical habitat in areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species. For example, an area that was not occupied at the time of listing but is essential to the conservation of the species may be included in the critical habitat designation. We designate critical habitat in areas outside the geographical area occupied by a species only when a designation limited to its range would be inadequate to ensure the conservation of the species (50 CFR 424.12(e)).

Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific and commercial data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in the Federal Register on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658)), and our associated Information Quality Guidelines, provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.

When we are determining which areas should be designated as critical habitat, our primary source of information is generally the information developed during the listing process for the species. Additional information sources may include the recovery plan for the species, articles in peer-reviewed journals, conservation plans developed by States and counties, scientific status surveys and studies, biological assessments, other unpublished materials, or experts' opinions or personal knowledge.

Habitat is dynamic, and northern spotted owls may move from one area to another over time. We recognize that critical habitat designated at a particular point in time may not include all of the habitat areas that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be needed for recovery of the species. Areas that are important to the conservation of the species, both inside and outside the critical habitat designation, will continue to be subject to: (1) Conservation actions implemented under section 7(a)(1) of the Act, (2) regulatory protections afforded by the requirement in section 7(a)(2) of the Act for Federal agencies to insure their actions are not likely to jeopardize the continued existence of any endangered or threatened species, and (3) the prohibitions of section 9 of the Act. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. These protections and conservation tools will continue to contribute to recovery of this species. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans (HCPs), or other species conservation planning efforts if new information available at the time of these planning efforts calls for a different outcome.

In accordance with section 3(5)(A)(i) and 4(b)(1)(A) of the Act and regulations at 50 CFR 424.12, in determining which areas within the geographical area occupied by the species at the time of listing to designate as critical habitat, we consider the physical or biological features essential to the conservation of the species and which may require special management considerations or protection. These include, but are not limited to:

(1) Space for individual and population growth and for normal behavior;

(2) Food, water, air, light, minerals, or other nutritional or physiological requirements;

(3) Cover or shelter;

(4) Sites for breeding, reproduction, or rearing (or development) of offspring; and

(5) Habitats that are protected from disturbance or are representative of the historical, geographical, and ecological distributions of a species.

For the northern spotted owl, the physical or biological features essential to the owl are forested areas that are used or likely to be used by northern spotted owl for nesting, roosting, foraging, or dispersing. The specific characteristics or components that comprise these features include, for example, specific ranges of forest stand density and tree size distribution; coarse woody debris; and specific resources, such as food (prey and suitable prey habitat), nest sites, cover, and other physiological requirements required by northern spotted owls and considered essential for the conservation of the species. We consider these specific primary constituent elements (PCEs) later; here we describe the life-history needs of the owl and the physical and biological features essential to the conservation of the northern spotted owl, which informed our identification of the PCEs. The following information is based on studies of the habitat, ecology, and life history of the species as described in the final listing rule published in the Federal Register on June 26, 1990 (55 FR 26114), the Revised Recovery Plan for the Northern Spotted Owl released on June 30, 2011, the Background section of this proposal, and the following information.

Although the northern spotted owl is typically considered a habitat and prey specialist, it uses a relatively broad array of forest types for nesting, roosting, foraging, and dispersal. The diversity of forest types used is a reflection of the large geographical range of this subspecies and strong gradation in annual precipitation and temperature associated with both coastal mountain ranges and the Cascade Range. While the northern spotted owl is unquestionably associated with old-growth forests, habitat selection and population performance involves many additional features (Loehle et al. 2011, p. 20). This description of physical and biological features summarizes both variation in habitat use and particular features or portions of the overall gradient of variation that spotted owls preferentially select, and that we, therefore, consider essential to their conservation. We begin by considering the broad-scale patterns of climate, elevation, topography, and forest community type that act to influence spotted owl distributions and space for population growth and dispersal, and then discuss the abundance and pattern of habitats used for nesting, roosting, and foraging at the landscape scale that influence the availability and occupancy of breeding sites and the survival and fecundity of spotted owls. Thus, we begin by considering factors that operate at broader spatial scales and proceed to factors that influence habitat quality at the stand scale. When we discuss the physical or biological features, we focus on features that are common rangewide, but also summarize specific features or patterns of habitat selection that characterize particular regions.

Climate, elevation, and topography are features of the physical environment that influence the capacity of a landscape to support habitat with high value for spotted owls and the type of habitat needed by the species. The distribution and amount of habitat on the landscape reflects interactions among these physical elements. Several studies have found that physical aspects of the environment such as topographic position, aspect, and elevation influence spotted owl habitat selection (e.g., Clark 2007, pp. 97-111; Stalberg et al. 2009, p. 80). They also are a factor in determining the type of habitats essential to spotted owl conservation.

Population processes for spotted owls are affected by both large-scale fluctuations in climate conditions and by local weather variation (Glenn 2009, pp. 246-248). The influence of weather and climate on spotted owl populations has been documented in northern California (Franklin et al. 2000, pp. 559-583), Oregon (Olson et al. 2004, pp. 1047-1052; Dugger et al. 2005, pp. 871-877; Glenn et al. 2010, pp. 2546-2551), and Washington (Glenn et al. 2010, pp. 2546-2551). Climate and weather effects on spotted owls are mediated by vegetation conditions, and the combination of climate and vegetation variables improves models designed to predict the distribution of spotted owls (e.g., Carroll 2010, pp. 1434-1437).

Climate niche models for the spotted owl identified winter precipitation as the most important climate variable influencing ability to predict the distribution of spotted owl habitat (Carroll 2010, p. 1434), a finding consistent with previous demographic studies that suggest negative effects of winter and spring precipitation on survival, recruitment, and dispersal (Franklin et al. 2000; pp. 559-583). Niche modeling suggested that precipitation variables, both in winter and in summer, were more influential than winter and summer temperatures (Carroll 2010, p. 1434-1436).

Wet, cold weather during the winter or nesting season, particularly the early nesting season, has been shown to negatively affect spotted owl reproduction (Olson et al. 2004, p.1039; Dugger et al. 2005, p.863; Glenn et al. 2011b, p. 1279), survival (Franklin et al. 2000, p. 539;, Olson et al. 2004, p. 1039; Glenn et al. 2011a, p. 159), and recruitment (Franklin et al. 2000 p. 559; Glenn et al. 2010, p. 2546). Cold, wet weather may reduce reproduction and/or survival during the breeding season due to declines or decreased activity in small mammal populations so that less food is available during reproduction when metabolic demands are high (Glenn et al. 2011b, pp. 1290-1294). Wet, cold springs or intense storms during this time may increase the risk of starvation in adult birds (Franklin et al. 2000, pp. 559-590). Cold, wet weather may also reduce the male spotted owl's ability to bring food to incubating females or nestlings (Franklin et al. 2000, pp. 559-590). Cold, wet nesting seasons have been shown to increase the mortality of nestlings due to chilling (Franklin et al. 2000, pp. 559-590) and reduce the number of young fledged per pair per year (Franklin et al. 2000, p. 559, Olson et al. 2004, p. 1047; Glenn et al. 2011b, 1279). Wet, cold weather may decrease survival of dispersing juveniles during their first winter, thereby reducing recruitment (Franklin et al. 2000, pp.559-590).

Franklin et al. (2000, pp. 582-583) argued that spotted owl populations are regulated or limited by both habitat quality and environmental factors such as weather. Abundance and availability of prey may ultimately limit spotted owl populations, and prey are strongly associated with habitat conditions. As habitat quality decreases, other factors such as weather have a stronger influence on demographic performance. In essence, the presence of high-quality habitat appears to buffer the negative effects of cold, wet springs and winters on survival of spotted owls as well as ameliorate the effects of heat. High-quality spotted owl habitat was defined in a northern California study area as a mature or old growth core within a mosaic of old and younger forest (Franklin et al. 2000, p.559). The high-quality habitat can help maintain a stable prey base, thereby reducing the cost of foraging during the early breeding season when energetic needs are high (Carey et al. 1992, pp. 223-250; Franklin et al. 2000, p. 559). In addition, mature and old forest with high canopy closure typically remains cooler during summer months than younger stands.

Drought or hot temperatures during the previous summer have also been associated with reduced spotted owl recruitment and survival (Glenn et al. 2010, p. 2546). Drier, warmer summers and drought conditions during the growing season strongly influence primary production in forests, food availability, and the population sizes of small mammals (Glenn et al. 2010, p. 2546). Northern flying squirrels, for example, forage primarily on ectomycorrhizal fungi (truffles), many of which grow better under moist conditions (Lehmkuhl et al. 2004, pp. 58-60). Drier, warmer summers, or the high-intensity fires, which such conditions support, may change the range or availability of these fungi, affecting northern flying squirrels and the spotted owls that prey on them. Periods of drought are associated with declines in annual survival rates for other raptors due to a presumed decrease in prey availability (Glenn et al. 2010, pp. 2546-2551).

Mexican spotted owls ( S. o. lucida ) and California spotted owls ( S. o. occidentalis ) have a narrow temperature range where body temperature can be maintained without additional metabolic energy expenditure (Ganey et al. 1993, pp. 653-654; Weathers et al. 2001, pp. 682-686). Others (e.g., Franklin et al. 2000, entire) have assumed the northern spotted owl to be similar in this regard. While winter temperatures are relatively mild across much of the northern spotted owl's range, heat stress has been identified as a potential stressor at temperatures exceeding 30 °C (86 °F; Weathers et al. 2001, p. 678). The spotted owl's selection for areas with older-forest characteristics has been hypothesized to be related, in part, to its needing cooler areas in summer to avoid heat stress (Barrows and Barrows 1978, entire).

Elevation and corresponding changes in temperature/moisture regimes constrain the development of vegetation communities selected by spotted owls, and may exceed the bounds of physiological tolerance of spotted owls or their prey. Several studies have noted the avoidance or absence of spotted owls above location-specific elevational limits (Blakesley et al. 1992, pp. 390-391; Hershey et al. 1998, p. 1406; LaHaye and Gutiérrez 1999, pp. 326, 328). In some locations, elevational limits occur despite the presence of forests that appear to have the structural characteristics typically associated with spotted owl habitat. Where forest structure is not the apparent cause of elevational limits, the mechanistic bases of these limits are unknown, but they could be related to prey availability, competitors, or extremes of temperature or precipitation. Habitat for spotted owls can occur from sea level to the lower elevation limit of subalpine vegetation types. This elevation varies with latitude from about 3,000 feet (ft) (900 meters (m)) above sea level in coastal Washington and Oregon (Davis and Lint 2005, p. 32) to about 6,000 ft (1,800 m) above sea level near the southern edge of the range (derived from Davis and Lint 2005, p. 32).

Topography also influences the distribution of spotted owl habitat and patterns of habitat selection. The effects of topography are strongest in drier forests where aspect and insolation (amount of solar radiation received in an area) contribute to moisture stress that can limit forest density and tree growth. In drier forests east of the Cascades and in the Klamath region, suitable habitat can be concentrated at intermediate topographic positions, on north-facing aspects, and in concave landforms that retain moisture. This leads to a distribution of suitable habitat characterized by ribbon-like bands and discrete patches. Ribbons occur along drainages and valley bottoms, along the north faces of ridges that trend from east to west, and at intermediate topographic positions between drier pine-dominated forests at lower elevations and subalpine forest types at higher elevations. Discrete patches occur on top of higher plateaus and in concave landforms. Spotted owl populations inhabiting drier forests have higher fecundity and lower survival rates than owls in other regions (Hicks et al. 2003, pp. 61-62; Anthony et al. 2006, pp. 28, 30;). The naturally fragmented distribution of suitable habitat in drier forests and increased predation risk associated with traversing this landscape may be one of many features that contributed to the evolution of these life-history characteristics.

Slope may also influence the distribution of suitable habitat. Intermediate slopes have been associated with spotted owl sites in some studies (e.g., Gremel 2005, p. 37; Gaines et al. 2010, pp. 2048-2050; USFWS 2011, Appendix C), but the mechanisms underlying this association are unclear, potentially including a variety of features from soil depth to competition with barred owls.

Across their geographical range, spotted owl use of habitat spans several scales, with increasing levels of habitat selection specificity at each scale. We refer to these scales as the “landscape,” “home range,” and “core area” scales. Nest stands within core areas are even more narrowly selected (see Functional Categories of Spotted Owl Habitat, in the Background section, above).

Landscapes supporting populations of spotted owls are the broadest scale we will consider, encompassing areas sufficient to support numerous reproductive pairs (roughly 20,000 to 200,000 ac (8,100 to 81,000 ha). Within landscapes, the northern spotted owl inhabits most of the major types of coniferous forests across its geographical range, including Sitka spruce, western hemlock, mixed conifer and mixed evergreen, grand fir, Pacific silver fir, Douglas-fir, redwood/Douglas-fir (in coastal California and southwestern Oregon), white fir, Shasta red fir, and the moist end of the ponderosa pine zone (Forsman et al. 1984, pp. 8-9; Franklin and Dyrness 1988, numerous pages; Thomas et al. 1990, p. 145). These forest types may be in early-, mid-, or late-seral stages, and must occur in concert with at least one of the physical or biological features characteristic of breeding and nonbreeding (dispersal) habitat, described below.

Landscape-level patterns in tree species composition and topography can influence the distribution and density of spotted owls. These differences in spotted owl distribution occur even when different forest types have similar structural attributes, suggesting that spotted owls may prefer specific plant associations or tree species. Some forest types, such as pine-dominated and subalpine forests, are infrequently used, regardless of their structural attributes. In areas east of the Cascade Crest, spotted owls select forests with high proportions of Douglas-fir trees. The effects of tree species composition on habitat selection also extend to hardwoods within conifer-dominated forests (e.g., Meyer et al. 1998, p. 35). For example, our habitat association modeling indicated that habitat value in the central Western Cascades was negatively related to proportion of hardwoods present. At the home range and core area scales, locations occupied by spotted owls consistently have greater amounts of mature and old-growth forest compared to random locations or unused areas. The proportion of older forest within the home range varies greatly by geographical region, but typically falls between 30 and 78 percent (Courtney et al. 2004, p. 5-6). The only exception to this pattern occurred in drier forests of Washington, where development of a dense understory of shade-tolerant trees may have reduced suitability of older forests subjected to prolonged fire exclusion (Irwin et al. 2004, p. 20). In studies where circles of different sizes were compared, differences between spotted owl sites and random locations diminished as circles of increasing size were evaluated (Courtney et al. 2004, p. 5-7), suggesting habitat selection is stricter at the core area scale than at the home range and landscape scales.

Natural disturbances and anthropogenic (human-caused) activities continuously shape the amount and distribution of spotted owl habitat on the landscape. In moist forests west of the Cascades in Washington and Oregon, and in the Redwood region, anthropogenic activities have a dominant influence on distribution patterns of remaining habitat, with natural disturbances typically playing a secondary role. In contrast, drier forests east of the Cascades and in the Klamath region have dynamic disturbance regimes that continue to exert a strong influence on spotted owl habitat. Climate change may modify disturbance regimes across the range of the spotted owl, resulting in substantial changes to the frequency and extent of habitat disruption by natural events.

In drier forests, low- and mixed-severity fires historically contributed to a high level of spatial and temporal variability in landscape patterns of disturbed and recovering vegetation. However, anthropogenic activities have so altered these historic patterns of vegetation and fuels and associated disturbance regimes that contemporary landscapes no longer function as they did historically (Hessburg et al. 2000a, pp. 77-78; Hessburg and Agee 2003, pp. 44-51; Hessburg et al. 2005, pp. 122-127, 134-136; Skinner et al. 2006, pp. 176-179; Skinner and Taylor 2006, pp. 201-203).

Fire exclusion, combined with the removal of fire-tolerant structures (e.g. , large, fire-tolerant tree species such as ponderosa pine, western larch ( Larix occidentalis ), and Douglas-fir), have reduced the resiliency of the landscape to fire and other disturbances, especially in those forest types outside of the wetter, higher severity fire regime types (Agee 1993, pp. 280-319; Hessburg et al. 2000a, pp. 71-80; Hessburg and Agee 2003, pp. 44-46). Understory vegetation in these forests has shifted in response to fire exclusion from grasses and shrubs to shade-tolerant conifers, reducing fire tolerance of these forests and increasing drought stress on dominant tree species.

Anthropogenic activities have also fundamentally changed the spatial distribution of fire intolerant-stands among the fire-tolerant stands, changing the pattern of fire activity across the landscape. Past management has homogenized the formerly patchy vegetative network and reduced the complexity that was more prevalent during the pre-settlement era (Skinner 1995, pp. 224-226; Hessburg and Agee 2003, pp. 44-45; Hessburg et al. 2007, p. 21; Kennedy and Wimberly 2009, pp. 564-565). Patches of fire-intolerant vegetation that had been spatially separated have become more contiguous and are more prone to conducting fire, insects, and diseases across larger swaths of the landscape (Hessburg et al. 2005, pp. 71-74, 77-78). This homogenized landscape may be altering the size and intensity of current disturbances and further altering landscape functionality (e.g. , Everett et al. 2000, pp. 221-222). This alteration in the disturbance regime further affects forest structure and composition.

The intensity and spatial extent of natural disturbances that affect the amount, distribution, and quality of spotted owl habitat in dry forests are also influenced by local topographic features, elevation, and climate (Swanson et al. 1988, entire). At local scales these factors can be used to identify refugia that are insulated from existing disturbance and consequently tend to persist for longer periods (Camp et al. 1997, entire). These disturbance refugia are locations where spotted owl habitat has a higher likelihood of developing and persisting in drier forests. As a result of these disturbance regimes, especially in the drier forests within its range, habitat for the northern spotted owl naturally occurs in a patchy mosaic in various stages of suitability in these regions. Sufficient area to provide for these habitat dynamics and to allow for the maintenance of adequate quantities of suitable habitat on the landscape at any one point in time is, therefore, essential to the conservation of the northern spotted owl in the dry forest regions.

Historically, forest types occupied by the northern spotted owl were fairly continuous, particularly in the wetter parts of its range in coastal northern California and most of western Oregon and Washington. Suitable forest types in the drier parts of the range (interior northern California, interior southern Oregon, and east of the Cascade crest in Oregon and Washington) occur in a mosaic pattern interspersed with infrequently used vegetation types such as open forests, shrubby areas, and grasslands. As described above, natural disturbance processes in these drier regions likely contributed to a pattern in which patches of habitat in various stages of suitability shift positions on the landscape through time. In the Klamath Mountains Provinces of Oregon and California, and to a lesser extent in the Coast and Cascade Provinces of California, large areas of serpentine soils exist that are typically not capable of supporting northern spotted owl habitat (Davis and Lint 2005, pp. 31-33).

We have described a range of climatic, elevational, topographic, and compositional factors, and associated disturbance dynamics typical of different regions, that constrain the amount and distribution of spotted owl habitat across landscapes. Within this context, areas that contain the physical and biological features described below must provide habitat in an amount and distribution sufficient to support persistent populations, including metapopulations of reproductive pairs, and opportunities for nonbreeding and dispersing owls to move among populations to be considered essential to the conservation of the northern spotted owl.

Spotted owls are territorial, defending areas that vary across nearly an order of magnitude, from about 1,400 to 14,000 ac (570 to 5,700 ha), depending on latitude and prey resources (see Home Range Requirements, below). Overlap occurs among adjoining territories, but the large size of territories nonetheless means that populations of spotted owls require landscapes with large areas of habitat suitable for nesting, roosting, and foraging. For example, in the northern parts of the subspecies' range where territories are largest, a population of 20 resident pairs would require at least 100,000 ac (about 40,500 ha) when habitat is relatively densely distributed and of high-quality.

As described in the Background section above, several studies have examined patterns of spotted owl habitat selection at the territory scale and the consequences of habitat configuration within a territory on fitness. We do not know if the features that contribute to enhancing spotted owl occupancy and reproductive success at the territory scale can be scaled up to predict what landscape-scale patterns of habitat are most conducive to stable or increasing spotted owl populations. Studies that use populations as units of analysis in order to investigate the effects of the landscape-scale configuration of habitat on the performance of spotted owl populations have only begun. Past models of spotted owl population dynamics have included predictions about the effects of habitat configuration on population performance, but these predictions have not been tested or validated by empirical studies (Franklin and Gutiérrez 2002; p. 215). Recent demographic analyses suggested that recruitment was positively related to the proportion of study areas covered by suitable habitat (see Forsman et al. 2011, pp. 59-62), but this covariate was not associated with other aspects of demographic performance, and few other covariates were investigated.

When the spotted owl was listed as threatened in 1990 (55 FR 26114), habitat loss and fragmentation of old-growth forest were identified as major factors contributing to declines in spotted owl populations. As older forests were reduced to smaller and more isolated patches, the ability of spotted owls to successfully disperse and establish territories was likely reduced (Lamberson et al. 1992, pp. 506, 508, 510-511). Lamberson et al. (1992, pp. 509-511) identified that there appeared to be a sharp threshold in the amount of habitat below which spotted owl population viability plummeted. Lamberson et al. (1994, pp. 185-186, 192-194) concluded that size, spacing and shape of reserved areas all had strong influence on population persistence, and reserves that could support a minimum of 20 spotted owl territories were more likely to maintain spotted owl populations than smaller reserves. They also found that juvenile dispersal was facilitated in areas large enough to support at least 20 spotted owl territories. In addition to size, spacing between reserves had a strong influence on successful dispersal (Lamberson et al. 1992, pp. 508, 510-511). Forsman et al. (2002, pp. 15-16) reported dispersal distances of 1,475 spotted owls in Oregon and Washington for 1985 to 1996. Median maximum dispersal distance (the straight-line distance between the natal site and the farthest location) for radio-marked juvenile male spotted owls was 12.7 miles (mi) (20.3 kilometers (km)), and that of female spotted owls was 17.2 mi. (27.5 km) (Forsman et al. 2002: Table 2). Dispersal data and other studies on the amount and configuration of habitat necessary to sustain spotted owls provided the foundation for developing previous spotted owl habitat reserve systems. Given the range-wide declining trends in northern spotted owl populations as well as declining trends in the recruitment of new individuals into territorial populations (Forsman et al. 2011, pp. 59-66, Table 22), we have determined that, to be essential, physical and biological features must be positioned on the landscape to enable populations to persist and individual owls to disperse among populations.

In contrast to earlier designations of critical habitat, we did not develop an a priori rule set to identify those areas that provide the physical or biological features essential to the conservation of the owl, using factors such as minimum size of habitat blocks, targeted numbers of owl pairs, or maximum distance between blocks of habitat. Instead, we determined the spatial extent and placement of the areas providing the physical or biological features that are essential to the conservation of the owl based on the relative demographic performance of various habitat models tested. This process is summarized in Criteria Used to Identify Critical Habitat, below, and is presented in detail in our supporting documentation (Dunk et al. 2012, entire).

Northern spotted owls remain on their home range throughout the year; therefore, their home range must provide all the habitat components and prey needed for the survival and successful reproduction of a territorial pair. The home range of a northern spotted owl is relatively large, but varies in size across the range of the subspecies (Courtney et al. 2004, p. 5-24; 55 FR 26117, June 26, 1991). Home range sizes are largest in Washington (Olympic Peninsula: 14,271 ac (5775 ha) (USDI 1992, p. 23; USFWS 1994 in litt., p. 1) and generally decrease along a north-south gradient to approximately 1,430 ac (580 ha) in the Klamath region of northwestern California and southern Oregon (Zabel et al. 1995, p. 436). Northern spotted owl home ranges are generally larger where northern flying squirrels are the predominant prey and smaller where woodrats are the predominant prey (Zabel et al. 1995, p. 436). Home range size also increases with increasing forest fragmentation (Carey et al. 1992, p. 235; Franklin and Gutiérrez 2002, p. 212; Glenn et al. 2004, p. 45) and decreasing proportions of nesting habitat on the landscape (Carey et al. 1992, p. 235; Forsman et al. 2005, p. 374), suggesting that northern spotted owls increase the size of their home ranges to encompass adequate amounts of suitable forest types (Forsman et al. 2005, p. 374).

Meta-analysis of features associated with occupancy at the territory-scale indicated that spotted owls consistently occupy areas having larger patches of older forests (which contained more interior forest) that were more numerous and closer together than random sites (Franklin and Gutiérrez 2002; p. 212). In the Klamath and Redwood regions owls also consistently occupy sites with higher forest heterogeneity than random sites. Occupied sites in the Klamath region, in particular, show a high degree of vegetative heterogeneity, with more variable patch sizes and more perimeter edge than in other regions (Franklin and Gutiérrez 2002; p. 212). In the Klamath region, ecotones, or edges between older forests and other seral stages, may contribute to improved access to prey (Franklin and Gutiérrez 2002, p. 215). Several studies in the Klamath region and the Redwood region have found that variables describing the relationship between habitat core area and edge length improve the ability of models to predict spotted owl occupancy (e.g., Folliard et al. 2000, pp. 79-81; Zabel et al 2003, pp. 1936-1038). In contrast, spotted owl sites in the Oregon Coast Range had a more even distribution of cover types than random locations, and nest stands had a higher ratio of core to edge and more complex stand shapes than non-nest stands (Courtney et al. 2004, p. 5-9).

A home range provides the habitat components essential for the survival and successful reproduction of a resident breeding pair of northern spotted owls. The exact amount, quality, and configuration of these habitat types required for survival and successful reproduction varies according to local conditions and factors such as the degree of habitat fragmentation, proportion of available nesting habitat, and primary prey species (Courtney et al. 2004, p. 5-2).

Northern spotted owls often use habitat within their home ranges disproportionally, and exhibit central-place foraging behavior (Rosenberg and McKelvey 1999, p. 1028), with much activity centered within a core area surrounding the nest tree during the breeding season. During fall and winter, as well as in nonbreeding years, owls often roost and forage in areas of their home range more distant from the core. The size of core areas varies considerably across the subspecies' geographical range following a pattern similar to that of home range size (Bingham and Noon 1997, p. 133), varying from over 4,057 ac (1,642 ha) in the northernmost (flying squirrel prey) provinces (Forsman et al. 2005, pp. 370, 375) to less than 500 ac (202 ha) in the southernmost (dusky-footed woodrat prey) provinces (Pious 1995, pp. 9-10, Table 2; Zabel et al. 2003, pp. 1036-1038). Owls often switch nest trees and use multiple core areas over time, possibly in response to local prey depletion or loss of a particular nest tree.

Core areas contain greater proportions of mature/old forest than random or nonuse areas (Courtney et al. 2004, p. 5-13), and the amount of high-quality habitat at the core area scale shows the strongest relationships with occupancy (Meyer et al. 1998, p. 34; Zabel et al. 2003, pp. 1027, 1036), survival (Franklin et al. 2000, p. 567; Dugger et al. 2005, p. 873), and reproductive success (Ripple et al. 1997, pp. 155 to 156; Dugger et al. 2005, p. 871). In some areas, edges between forest types within northern spotted owl home ranges may provide increased prey abundance and availability (Franklin et al. 2000, p. 579). For successful reproduction, core areas need to contain one or more forest stands that have both the structural attributes and the location relative to other features in the home range that allow them to fulfill essential nesting, roosting, and foraging functions (Carey and Peeler 1995, pp. 233-236; Rosenberg and McKelvey 1999, pp. 1035-1037).

Northern spotted owls regularly disperse through highly fragmented forested landscapes that are typical of the mountain ranges in western Washington and Oregon, and have dispersed from the Coastal Mountains to the Cascades Mountains in the broad forested regions between the Willamette, Umpqua, and Rogue Valleys of Oregon (Forsman et al. 2002, p. 22). Corridors of forest through fragmented landscapes serve primarily to support relatively rapid movement through such areas, rather than colonization or residency of nonbreeding owls.

During the transience (movement) phase, dispersers used mature and old-growth forest slightly more than its availability; during the colonization phase, mature and old-growth forest was used at nearly twice its availability (Miller et al. 1997, p. 144). Closed pole-sapling-sawtimber habitat was used roughly in proportion to availability in both phases and may represent the minimum condition for movement. Open sapling and clearcuts were used less than expected based on availability during colonization (Miller et al. 1997, p. 145). This indicates that transient dispersers can use a greater variety of forested habitats relative to those subadults or nonbreeding adults that are residents; the latter individuals will require habitats that are more similar to the nesting, roosting, and foraging habitats utilized by breeding pairs.

We currently do not have sufficient information to permit formal modeling of dispersal habitat and the influence of dispersal habitat condition on dispersal success (USFWS 2011, p. C-15). We expect that dispersal success is highest when dispersers move through forests that have the characteristics of nesting-roosting and foraging habitats. Spotted owls can also disperse successfully through forests with less complex structure, but risk of starvation and predation likely increase with increasing divergence from the characteristics of suitable (nesting, roosting, foraging) habitat.

Relatively little information is currently available about the features of habitats used by dispersing spotted owls, or the effectiveness of different approaches to managing dispersal habitat. The suitability of habitat to contribute to successful dispersal of spotted owls is likely related to the degree to which it ameliorates heat stress, provides abundant and accessible prey, limits predation risk, and resembles habitat in natal territories (Carey 1985, pp. 105-107; Buchanan 2004, pp. 1335-1341).

Dispersal habitat is habitat that owls use when dispersing. Although no formal studies have been completed to characterize dispersal habitat, a widely-accepted rule of thumb is that while dispersal habitat would optimally be the same as suitable nesting, roosting, or foraging habitat (mature and old-growth stands), if necessary owls can also make use of young stands of trees approximately 11 inches (in) (28 centimeters (cm)) diameter at breast height (dbh) or greater with roughly a minimum 40 percent canopy closure. Dispersal habitat consists of forest types described above that provide one or both of the habitat components described below that are essential to the dispersal of juvenile and nonterritorial northern spotted owls. Dispersal habitat can occur between larger blocks of nesting, foraging, and roosting habitat or within blocks of nesting, roosting, and foraging habitat. Dispersal habitat is essential to maintaining stable populations by promoting rapid filling of territorial vacancies when resident northern spotted owls die or leave their territories, and to providing adequate gene flow across the range of the species.

Differences in patterns of habitat associations across the range of the spotted owl suggest four different broad zones of habitat use, which we characterize as the West Cascades/Coast Ranges of Oregon and Washington, East Cascades, Klamath and Northern California Interior Coast Ranges, and Redwood Coast (Figure 4). We configured these zones based on a qualitative assessment of similarity among ecological conditions and habitat associations within the 11 different regions analyzed, as these four zones efficiently capture the range in variation of some of the physical or biological features essential to the conservation of the northern spotted owl. We summarize the physical or biological features for each of these four zones, emphasizing zone-specific features that are distinctive within the context of general patterns that apply across the entire range of the northern spotted owl.

This zone includes five regions west of the Cascade crest in Washington and Oregon (Western Cascades North, Central and South; North Coast Ranges and Olympic Peninsula; and Oregon Coast Ranges; USFWS 2011, p. C-13). Climate in this zone is characterized by high rainfall and cool to moderate temperatures. Variation in elevation between valley bottoms and ridges is relatively low in the Coast Ranges, creating conditions favorable for development of contiguous forests. In contrast, the Olympic and Cascade ranges have greater topographic variation, with many high-elevation areas supporting permanent snowfields and glaciers. Douglas-fir and western hemlock dominate forests used by spotted owls. Root diseases and wind-throw are important natural disturbance mechanisms that form gaps in forested areas. Flying squirrels are the dominant prey, with voles and mice also representing important items in the spotted owl's diet.

Our habitat association modeling indicated that vegetation structure had a dominant influence on owl population performance, with habitat pattern and topography also contributing. High canopy cover, high density of large trees, high numbers of sub-canopy vegetation layers, and low to moderate slope positions were all important features.

Nesting habitat in this zone is mostly limited to areas with large trees with defects such as mistletoe brooms, cavities, or broken tops. The subset of foraging habitat that is not nesting/roosting habitat generally had slightly lower values than nesting habitat for canopy cover, tree size and density, and canopy layering. Prey species in this zone are associated with mature to late-successional forests, resulting in small differences between nesting, roosting, and foraging habitat.

This zone includes the Eastern Cascades North and Eastern Cascades South regions (USFWS 2011, p. C-13). This zone is characterized by a continental climate (cold, snowy winters and dry summers) and a high frequency of natural disturbances due to fires and outbreaks of forest insects and pathogens. Flying squirrels are the dominant prey species, but the diet of spotted owls also includes relatively large proportions of bushy-tailed woodrats, snowshoe hare, pika, and mice (Forsman et al. 2001, pp. 144-145).

Our modeling indicates that habitat associations in this zone do not show a pattern of dominant influence by one or a few variables (USFWS 2011, Appendix C). Instead, habitat association models for this zone included a large number of variables, each making a relatively modest contribution (20 percent or less) to the predictive ability of the model. The features that were most useful in predicting habitat quality were vegetation structure and composition, and topography, especially slope position in the north. Other efforts to model habitat associations in this zone have yielded similar results (e.g., Gaines et al. 2010, pp. 2048-2050; Loehle et al. 2011, pp. 25-28).

Relative to other portions of the subspecies' range, nesting and roosting habitat in this zone includes relatively younger and smaller trees, likely reflecting the common usage of dwarf mistletoe brooms (dense growths) as nesting platforms (especially in the north). Forest composition that includes high proportions of Douglas-fir is also associated with this nesting structure. Additional foraging habitat in this zone generally resembles nesting and roosting habitat, with reduced canopy cover and tree size, and reduced canopy layering. High prey diversity suggests relatively diverse foraging habitats are used. Topographic position was an important variable, particularly in the north, possibly reflecting competition from barred owls (Singleton et al. 2010, pp. 289, 292). Barred owls, which have been present for over 30 years in northern portions of this zone, preferentially occupy valley-bottom habitats, possibly compelling spotted owls to establish territories on less productive, mid-slope locations (Singleton et al. 2010, pp. 289, 292).

This zone includes the Klamath-Siskiyou West, Klamath-Siskiyou East, and Interior California Coast regions (USFWS 2011, p. C-13). This region in southwestern Oregon and northwestern California is characterized by very high climatic and vegetative diversity resulting from steep gradients of elevation, dissected topography, and large differences in moisture from west to east. Summer temperatures are high, and spotted owls occur at elevations up to 1,768 m (5,800 ft). Western portions of this zone support a diverse mix of mesic forest communities interspersed with drier forest types. Forests of mixed conifers and evergreen hardwoods are typical of the zone. Eastern portions of this zone have a Mediterranean climate with increased occurrence of ponderosa pine. Douglas-fir dwarf mistletoe ( Arceuthobium douglasii ) is rarely used for nesting platforms in the west, but commonly used in the east. The prey base for spotted owls in this zone is correspondingly diverse, but dominated by dusky-footed woodrats, bushy-tailed woodrats, and flying squirrels. Spotted owls have been well studied in the Klamath portion of this zone, but relatively little is known about spotted owl habitat use in the California Interior Coast Range portion of the zone. Our habitat association models for this zone suggest that vegetation structure and topographic features are nearly equally important in influencing owl population performance, particularly in the Klamath. High canopy cover, high levels of canopy layering, and the presence of very large dominant trees were all important features of nesting and roosting habitat. Compared to other zones, additional foraging habitat for this zone showed greater divergence from nesting habitat, with much lower canopy cover and tree size. Low to intermediate slope positions were strongly favored. In the eastern Klamath, presence of Douglas-fir was an important compositional variable in our habitat model (USFWS 2011, Appendix C).

This zone is confined to the northern California coast, and is represented by the Redwood Coast region (USFWS 2011, p. C-13). It is characterized by a maritime climate with moderate temperatures and generally mesic conditions. Near the coast, frequent fog delivers consistent moisture during the summer. Terrain is typically low-lying (0 to 900 m (0 to 3,000 ft)). Forest communities are dominated by redwood, Douglas-fir—tanoak ( Lithocarpus densiflorus ) forest, coast live oak ( Quercus agrifolia ), and tanoak series. Dusky footed woodrats are dominant prey items in this zone.

Habitat association models for this zone diverged strongly from models for other zones. Topographic variables (slope position and curvature) had a dominant influence with vegetation structure having a secondary role. Low position on slopes was strongly favored, along with concave landforms.