Daily Rules, Proposed Rules, and Notices of the Federal Government
The coordinates or plot points or both from which the maps are generated are included in the administrative record for this critical habitat designation and are available at
This final rule describes the revised critical habitat designation for the northern spotted owl under the Endangered Species Act of 1973, as amended (Act) (16 U.S.C. 1531
We, the U.S. Fish and Wildlife Service (Service), listed the northern spotted owl as threatened on June 26, 1990 (55 FR 26114), because of widespread loss of habitat across its range and the inadequacy of existing regulatory mechanisms to conserve it. We previously designated critical habitat for the northern spotted owl in 1992 and 2008. The 2008 designation (73 FR 47326, August 13, 2008) was subsequently challenged in court. In July 2009, the Federal Government requested voluntary remand of the 2008 revised critical habitat designation. On March 8, 2012, we published in the
Section 4(b)(2) of the Act states that the Secretary shall designate critical habitat on the basis of the best available scientific data after taking into consideration the economic impact, national security impact, and any other relevant impact of specifying any particular area as critical habitat. The critical habitat areas we are designating in this rule constitute our current best assessment of the areas that meet the
• Approximately 2,918,067 ac (1,180,898 ha) in 4 units and 26 subunits in Washington.
• Approximately 4,557,852 ac (1,844,496 ha) in 8 units and 58 subunits in Oregon.
• Approximately 2,102,050 ac (850,669 ha) in 5 units and 36 subunits in California.
• This designation increases previously designated critical habitat, including the addition of 272,026 ac (110,085 ha) ac of State lands. However, this final critical habitat designation is a decrease from the 13,962,449 ac (5,649,660 ha) identified as meeting the definition of critical habitat in the March 8, 2012 (77 FR 14062) proposed rule.
• We have also excluded areas of State and private land from this designation of critical habitat under section 4(b)(2) of the Act, as explained in the Exclusions section of this rule.
The Revised Recovery Plan for the Northern Spotted Owl (USFWS 2011; hereafter “Revised Recovery Plan”) recommends that land managers: (1) conserve older forest, high-value habitat, and areas occupied by northern spotted owls; and (2) actively manage forests to restore ecosystem health in many parts of the species' range. In developing this critical habitat designation, we also recognize the importance of the Northwest Forest Plan (NWFP) and its land management strategy for conservation of native species associated with old-growth and late-successional forest, including the northern spotted owl. The designation of areas as critical habitat does not change land use allocations or Standards and Guidelines for management under the NWFP, nor does this rule establish any management plan or prescriptions for the management of critical habitat. However, we encourage land managers to consider implementation of forest management practices recommended in the Revised Recovery Plan to restore natural ecological processes where they have been disrupted or suppressed (
We relied on the recovery criteria set forth in the Revised Recovery Plan for the Northern Spotted Owl (USFWS 2011) to determine what is essential to the conservation of the species; therefore we have identified a habitat network that meets the following criteria:
• Ensures sufficient habitat to support stable, healthy populations across the range, and also within each of the 11 recovery units;
• Ensures distribution of northern spotted owl populations across the range of habitat conditions used by the species;
• Incorporates uncertainty, including potential effects of barred owls, climate change, and wildfire disturbance risk; and
• Recognizes that these protections are meant to work in concert with other recovery actions, such as barred owl management.
To assist us in determining critical habitat, we integrated habitat and demographic information (relating to occupancy, survival, reproduction, and movement) to develop a modeling tool that assesses the distribution of habitat quality and population dynamics across the range, and provides a more accurate picture of where high-quality northern spotted owl habitat exists. This model synthesized more than 20 years of data from on-the-ground demographic surveys, and allowed for analysis of how northern spotted owl populations would fare under different habitat conservation scenarios. We determined what is essential to recovery of the northern spotted owl by evaluating the performance of each potential critical habitat scenario considered against the recovery needs of the owl.
• As per the Service's normal practice, we solicited public review and comment on this rulemaking action, using information thus gained to correct and refine our designation.
• We fully considered exclusion of private lands and State lands from the final revised critical habitat, consistent with the best available scientific and commercial information.
The Service appreciates, and is sensitive to, the potential for regulatory burden that may result from our designation of critical habitat for the northern spotted owl under the Act. Our analysis indicated that the revision of critical habitat could have relatively little incremental effect above and beyond the conservation measures already required as a result of its threatened species status under the Act, and thus is not expected to impose substantial additional regulatory burdens. The Service appreciates, and relies on the many partners we have in conservation, including private landowners, Tribes, States, and local governments, and strongly desires to promote conservation partnerships to conserve, protect, and enhance fish, wildlife, plants, and their habitats for the continuing benefit of the American people.
It is our intent to discuss only those topics directly relevant to the revised designation of critical habitat in this 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
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 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
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
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 fully 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 critical habitat as defined in section (3)(5)(A) of the Act, which are (i) the specific areas within the geographical area occupied by the species at the time it was listed that provide the physical or biological features essential for the conservation of the species, and which may require special management considerations or protection, and (ii) specific 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 designations, 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
The development of a critical habitat network for the northern spotted owl must take into account current uncertainties, such as those associated with barred owl impacts and climate change predictions (USFWS 2011, p. III-10). 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 rule (see Criteria Used to Identify Critical Habitat, below) and in our supporting documentation (Dunk
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). High-value habitat is defined in the Revised Recovery Plan for the Northern Spotted Owl (USFWS 2011) as habitat that is important for maintaining northern spotted owls on landscapes, including areas with current and historic use by northern spotted owls. We refer readers to the glossary (Appendix G) of the Revised Recovery Plan for definitions of forest stand conditions and habitat types discussed in this rule.
Accordingly, in this rule, we have identified areas of habitat occupied at the time of listing that provide the physical or biological features essential to the conservation of the northern spotted owl, and that may require special management considerations or protection. When occupied areas were not adequate to achieve essential recovery goals, we also identified some unoccupied areas as critical habitat for the northern spotted owl only upon a determination that such areas are essential to the conservation of the species (see the second part of the definition of critical habitat in section (3)(5)(a)(ii), which states that critical habitat also includes “specific areas outside the geographical area occupied by the species at the time of listing in accordance with the provisions of section 4 of this Act, upon a determination by the Secretary that such areas are essential for the conservation of the species.”) However, it is important to note that this revised designation of critical habitat does not include all sites where northern spotted owls are presently known to occur. The habitat modeling that we used, in part, to assist us in developing this 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 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
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 forest management strategies will be needed to achieve results in certain landscapes. Active adaptive forest 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 have designated a critical habitat network that was developed based on what we determined to be the areas containing the physical and biological features essential for the conservation of the northern spotted owl or are otherwise essential to owl conservation, after taking into consideration 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 or 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 or 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 or 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).
The U.S. Forest Service, which manages the great majority of areas being designated as revised northern spotted owl critical habitat, has prioritized restoring and maintaining natural ecological function and resiliency to its forest lands (Blate
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 moist old-growth conifer forest in the western portion, to a mix of conifers and hardwood trees in the Klamath region, to dry, fire-prone forests in the eastern Cascades. Thousands of species occur in these forest ecosystems, including other listed and sensitive species with very specific biological needs. In areas where prescribed management is needed to maintain ecosystem function, such management is often expensive, logistically difficult, and contentious (Thompson
We reference here the recommendations for habitat management as made in the Revised Recovery Plan for the Northern Spotted Owl (USFWS 2011). This discussion is provided primarily for consideration by Federal, State, local, and private land managers, as they make decisions on the management of forest land under their jurisdictions and through their normal processes. This critical habitat rule does not take any action or adopt any policy, plan or program in relation to active forest management.
It is important to understand the relationship between northern spotted owl critical habitat and the Northwest Forest Plan (NWFP). In brief, the designation of areas as critical habitat does not change land use allocations or Standards and Guidelines for management under the NWFP. Critical habitat for the northern 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 late-successional forest habitat on Federal lands across the range of the species (Thomas
In developing this critical habitat designation, the Service recognizes the importance of the NWFP as the overarching land management strategy for conservation of the northern spotted owl and other native species associated with old-growth and late-successional forest. The system of reserves within the NWFP is essential for the conservation and development of large areas of late-successional forest across the landscape; however, because the NWFP was designed to benefit multiple species not every acre of the late-successional reserves (LSRs) provide high-quality habitat for northern spotted owls. In addition, barred owls have become increasingly abundant in the Pacific Northwest and likely have a large effect on the continued decline of northern spotted owl populations. With barred owls now sharing the range of the northern spotted owl, conservation of northern spotted owls outside NWFP reserved areas is increasingly important for species recovery.
In our designation of critical habitat on Federal lands, we identified lands that contain the features essential to the conservation of the species including lands both within NWFP reserves and matrix that function as highly valuable northern spotted owl habitat. As noted above, designation as critical habitat does not change these land use allocations or Standards and Guidelines for management under the NWFP, and we fully recognize the ecological functions and land management goals of the different land use allocations as outlined under the NWFP. While the NWFP has been successful in conserving large blocks of late-successional forest (Thomas
1. Conserve old-growth trees and forests on Federal lands
2. Manage NWFP forests as dynamic ecosystems that conserve all stages of forest development (e.g., encompassing the range of conditions between early-seral and old-growth), 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.
It is our hope that management of critical habitat for the northern spotted owl will be compatible with these broader landscape management goals articulated by Thomas
As stated above, many areas of critical habitat do not require active management, and active forest management within such areas could negatively impact northern spotted owls. We are not encouraging land managers to consider active management in areas of high-quality owl habitat or occupied owl sites; rather, we encourage management actions that will maintain and restore ecological function where appropriate. In some areas, forest stands are not on a trajectory to develop into high-value habitat, ecological processes have been disrupted by human actions, or projected climate change is expected to further disrupt or degrade desired forest conditions. In these areas, land managers may choose to implement active management, as recommended in the Revised Recovery Plan for the Northern Spotted Owl (USFWS 2011), to improve ecological health and development of forest conditions more favorable to northern spotted owls and other biodiversity. For example, LSRs are to be managed to protect and enhance old-growth forest conditions (defined in the Revised Recovery Plan as forests that have accumulated specific characteristics related to tree size, canopy structure, snags, and woody debris and plant associations). According to the NWFP Standards and Guidelines (USDA and USDI 1994), no programmed timber harvest is allowed inside the reserves. However, thinning or other silvicultural treatments inside these reserves may occur in younger stands if the treatments are beneficial to the creation and maintenance of late-successional forest conditions. On the east of the Cascades and in Oregon and California Klamath Provinces, additional management activities may be considered both within and outside reserves to reduce risks of large-scale disturbance (NWFP Standards and Guidelines, p. C-12—C-13).
We also recognize that ecological restoration is not the management goal on all NWFP land use allocations (
Mimicking natural disturbance regimes, such as fire, is an important strategy in North American forest management (Seymour and Hunter 1999, p. 56; Long 2009, p. 1868; Gustafsson
Specifically prescribing such management is beyond the scope or purpose of this document, and should instead be developed by the appropriate land management agency at the appropriate land management scale (e.g., National Forest or Bureau of Land Management District) (USDA 2010, entire; Fontaine and Kennedy 2012, p. 1559; Gustafsson
Some general considerations for managing for the conservation of essential physical or biological features within northern spotted owl critical habitat are discussed in more detail in the
In general, actions that promote ecological restoration and those that apply ecological forestry principles at appropriate scales as described above and in the Revised Recovery Plan for the Northern Spotted Owl (USFWS 2011, pp. III-11 to III-41) may be, in the right circumstances, consistent with the conservation of the northern spotted owl and the management of its critical habitat. However, we emphasize that this rule does not take any action or adopt any policy, plan or program in relation to active forest management. The discussion is provided only for consideration by Federal, State, local and private land managers, as well as the public, as they make decisions on the management of forest land under their jurisdictions and through their normal processes.
The Service supports the goals of maintaining and restoring ecological function and development of future northern spotted owl habitat. We encourage land managers to consider a stronger focus on ecological forestry in areas where commercial harvest and restoration are planned. We recognize the need to balance both the conservation of current owl sites and the development of future owl habitat. However, a better understanding of how ecological forestry approaches affect owls and their prey is needed. Studies have shown negative effects of commercial thinning and other conventional forestry practices on both northern spotted owls (Forsman
Given these concerns, and recognizing that appropriate management actions will vary depending upon site-specific conditions, we provide the following suggestions regarding active forest management for consideration by land managers within critical habitat as consistent with the recommendations of the Revised Recovery Plan for the Northern Spotted Owl:
1. Focus active management in younger forest, lower quality owl habitat, or where ecological conditions are most departed from the natural or desired range of variability.
2. In moist forests on Federal lands, follow NWFP guidelines as informed by the Revised Recovery Plan and focus on areas outside of LSRs (i.e., matrix). In dry forests, follow NWFP guidelines and focus on lands in or outside of reserves
3. Avoid or minimize activities in active northern spotted owl territories (or the high-quality habitat within these territories).
4. Ensure transparency of process so the public can see what is being done, where it is done, what the goal of the action is, and how well the action leads to the desired goal.
5. Practice active adaptive forest management by incorporating new information and learning into future actions to make them more effective, focusing on how these actions affect northern spotted owls and their prey.
Towards this objective of learning critical new scientific insights from research and adaptive management, we especially encourage research and active adaptive forest management on the seven Forest Service Experimental Forests (H.J. Andrews Experimental Forest, Pringle Falls Experimental Forest, South Umpqua Experimental Forest, and Cascades Head Experimental Forest in Oregon; Wind River Experimental Forest and Entiat Experimental Forest in Washington; and Yurok Redwood Experimental Forest in California) within designated northern spotted owl critical habitat. We acknowledge the specific value and contributions of research done within experimental forests in furtherance of the research and active adaptive forest management objectives in the Revised Recovery Plan. These Experimental Forests have four principal scientific advantages that support the specific kinds of research needed to better understand how management affects and potentially enhances northern spotted owl habitat:
(1) These sites are intended for and enabled to conduct manipulative research to test forest management strategies in a rigorous scientific manner;
(2) They have long-term baseline datasets that enable detailed climate/environmental change assessments;
(3) The sites represent a diversity of forest types within the range of northern spotted owl; and
(4) Experimental forests have been the subject of intensive, long-term study that can serve as a backdrop for new research.
Essential research and active adaptive forest management questions, detailed in the Revised Recovery Plan, that could be conducted on Experimental Forests include (but are not limited to):
(a) What vegetation management treatments best accelerate the development of forest structure associated with northern spotted owl habitat functions while maintaining or restoring natural disturbance and provide greater ecosystem resiliency?
(b) What are the effects of wildland and prescribed fire on the structural elements of northern spotted owl habitat?
(c) Can strategically-placed restoration treatments be used to reduce the risk of northern spotted owl habitat being burned by high severity fire within dry forest ecosystems?
(d) What are the effects of epidemic forest insect outbreaks on northern spotted owl occupancy and habitat use immediately following the event and at specified time periods after treatment?
Sound scientific information represents a vital component of our path to recovery for the northern spotted owl (and almost all threatened or endangered species). We believe it would be counterproductive to inhibit or curtail research that is designed to benefit the northern spotted owl and the ecosystem in which it is found, and therefore support research activities within experimental forests.
The northern spotted owl is a medium-sized owl and the largest of the three subspecies of northern spotted owls currently recognized by the American Ornithologists' Union (Gutiérrez
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 a threatened species under the Act throughout its range (55 FR 26114; June 26, 1990). Within the United States, the northern spotted owl ranges across 12 ecological regions, 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
For the purposes of developing this rule, and based on Appendix C of the Revised Recovery Plan for the Northern Spotted Owl (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 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 based on specific patterns of northern spotted owl habitat relationships and prey base relationships across the range of the species. The 11 regions include the North Coast Olympics; West Cascades North; West Cascades Central; West Cascades South; East Cascades North; East Cascades South; Oregon Coast; Klamath West; Klamath East; Redwood Coast; and Inner California Coast Ranges. We additionally grouped these 11 regions into 4 broad ecological zones (West Cascades/Coast Ranges of Oregon and Washington; East Cascades; Redwood; and Klamath and Northern California Interior Coast Ranges). A map of the 11 regions used for the purposes of habitat modeling, as well as the 4 ecological zones, is provided in Figure 1 of this document. We used these 11 regions as the organizing units for our designation of critical habitat, and the 4 ecological zones for the identification of region-specific primary constituent
Northern 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 northern 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 northern 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 late-seral or old-growth forest in the core area (Swindle
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 cover to provide protection from avian predators and at least minimal foraging opportunities (57 FR 1805, January 15, 1992). In this rule, we consider canopy cover as a vertical measurement of the amount of canopy that would cover the ground.
The three essential functions served by habitat within the home range of a northern spotted owl are: