Endangered and Threatened Wildlife and Plants; Proposed Revised Designation of Critical Habitat for the Northern Spotted Owl (Strix occidentalis caurina, 32450-32516 [07-2805]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 72, Number 112 (Tuesday, June 12, 2007)]
[Proposed Rules]
[Pages 32450-32516]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 07-2805]



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Part III





Department of the Interior





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Fish and Wildlife Service



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50 CFR Part 17



Endangered and Threatened Wildlife and Plants; Proposed Revised 
Designation of Critical Habitat for the Northern Spotted Owl (Strix 
occidentalis caurina); Proposed Rule

Federal Register / Vol. 72, No. 112 / Tuesday, June 12, 2007 / 
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AU37


Endangered and Threatened Wildlife and Plants; Proposed Revised 
Designation of Critical Habitat for the Northern Spotted Owl (Strix 
occidentalis caurina)

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to 
revise the critical habitat designation for the northern spotted owl 
(Strix occidentalis caurina) under the Endangered Species Act of 1973, 
as amended (Act). In 1992, we designated critical habitat for the 
northern spotted owl on 6,887,000 acres (ac) (2,787,070 hectares (ha)) 
of Federal lands in California, Oregon, and Washington. In this 
document we propose revised critical habitat for the northern spotted 
owl on a total of approximately 5,337,839 acres (ac) (2,160,194 
hectares (ha)) of Federal lands in California, Oregon, and Washington. 
If adopted, this action would result in a net decrease of approximately 
1,549,161 ac (626,915 ha) of designated critical habitat for the 
northern spotted owl.

DATES: We will accept comments from all interested parties until August 
13, 2007. We must receive requests for public hearings, in writing, at 
the address shown in the ADDRESSES section by July 27, 2007.

ADDRESSES: If you wish to comment, you may submit your comments and 
materials concerning this proposal by any one of several methods:
    1. You may mail or hand-deliver written comments and information to 
Kemper McMaster, Field Supervisor, U.S. Fish and Wildlife Service, 
Oregon Fish and Wildlife Office, 2600 SE 98th Ave., Suite 100, 
Portland, OR 97266.
    2. You may send comments by electronic mail (e-mail) to 
northernspottedowlCH@fws.gov. Please see the Public Comments Solicited 
section below for file format and other information about electronic 
filing.
    3. You may fax your comments to our Oregon Fish and Wildlife Office 
at 503-231-6195.
    4. You may go to the Federal eRulemaking Portal: https://
www.regulations.gov. Follow the instructions provided for submitting 
comments.
    Comments and materials received, as well as supporting 
documentation used in the preparation of this proposed rule, will be 
available for public inspection, by appointment, during normal business 
hours at the Oregon Fish and Wildlife Office, at the address above; the 
Western Washington Fish and Wildlife Office, 510 Desmond Drive SE., 
Suite 101, Lacey, WA 98503; and the Yreka Fish and Wildlife Office, 
1829 S. Oregon St., Yreka, CA 96097.

FOR FURTHER INFORMATION CONTACT: Kemper McMaster, Field Supervisor, 
Oregon Fish and Wildlife Office (see ADDRESSES) (telephone 503-231-
6179); Ken Berg, Field Supervisor, Western Washington Fish and Wildlife 
Office (see ADDRESSES) (telephone 360-753-9440); or Phillip Detrich, 
Field Supervisor, Yreka Fish and Wildlife Office (see ADDRESSES) 
(telephone 530-842-5763). People who use a telecommunications device 
for the deaf (TTD) may call the Federal Information Relay Service 
(FIRS) at 800-877-8339, 24 hours a day, 7 days a week.

SUPPLEMENTARY INFORMATION:

Public Comments Solicited

    We intend that any final action resulting from this proposal will 
be as accurate and as effective as possible. Therefore, comments or 
suggestions from the public, other concerned governmental agencies, the 
scientific community, industry, or any other interested party 
concerning this proposed rule are hereby solicited. Comments 
particularly are sought concerning:
    (1) The reasons why habitat should or should not be designated as 
critical habitat as provided by section 4 of the Act (16. U.S.C. 1531 
et seq.), including whether the benefit of designation would outweigh 
threats to the species caused by designation such that the designation 
of critical habitat is prudent;
    (2) Specific information on the amount and distribution of northern 
spotted owl habitat, what areas should be included in the revised 
designation that were occupied at the time of listing that contain the 
features that are essential for the conservation of the species and 
why, and what areas that were not occupied at the time of listing are 
essential to the conservation of the species and why;
    (3) Land use designations and current or planned activities in the 
subject areas and their possible impacts on proposed revised critical 
habitat;
    (4) Any foreseeable economic, national security, or other potential 
impacts resulting from the proposed revised designation and, in 
particular, any impacts on small entities; and the benefits of 
including or excluding areas that exhibit these impacts; and
    (5) Whether any areas should or should not be excluded from the 
revised designation under section 4(b)(2) of the Act and why; and
    (6) Whether our approach to designating critical habitat could be 
improved or modified in any way to provide for greater public 
participation and understanding, or to assist us in accommodating 
public concerns and comments.
    If you wish to comment, you may submit your comments and materials 
concerning this proposal by any one of several methods (see ADDRESSES 
section). Please submit e-mail comments to northernspottedowlCH@fws.gov 
in ASCII file format and avoid the use of special characters or any 
form of encryption. Please also include ``Attn: northern spotted owl 
critical habitat'' in your e-mail subject header. If you do not receive 
a confirmation from the system that we have received your message, 
contact us directly by calling our Oregon Fish and Wildlife Office at 
503-231-6179. Please note that the e-mail address 
nor0thernspottedowlCH@fws.gov will be closed out at the termination of 
the public comment period.
    Before including your address, phone number, e-mail address, or 
other personal identifying information in your comment, you should be 
aware that your entire comment--including your personal identifying 
information--may be made publicly available at any time. While you can 
ask us in your comment to withhold your personal identifying 
information from public review, we cannot guarantee that we will be 
able to do so.

Background

Ecological Considerations

Physical Description and Taxonomy
    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 (Gutierrez 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 
varied characteristics (reviewed in Courtney et al. 2004, pp. 3-3 to 3-
31), including genetic (Barrowclough and Guti[eacute]rrez 1990, p. 739; 
Barrowclough et al. 1999, p. 922; Haig et al. 2004b, p. 1353; 
Barrowclough et al. 2005, p.

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1113), morphological (Guti[eacute]rrez et al. 1995, pp. 2 to 3), 
behavioral (Van Gelder 2003, p. 30) and biogeographical information 
(Barrowclough et al. 1999, p. 928).

Distribution

    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 (USFWS 1990, pp. 
13, 60; June 26, 1990). The subspecies is listed as threatened under 
the Act throughout its range (55 FR 26114). Within the United States, 
the northern spotted owl ranges across 12 physiographic provinces, 
based on recognized landscape subdivisions exhibiting different 
physical and environmental features (Franklin and Dyrness 1988, pp. 5 
to 26; Thomas et al. 1990, p. 61; USDA and USDI 1994b, 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 1994b, p. A-3). 
Very few northern spotted owls are found in the Western Washington 
Lowlands or Willamette Valley, however, therefore the subspecies is 
restricted primarily to 10 of the 12 provinces within its range.
Population Status and Trends
    Demographic data, from studies initiated as early as 1985, have 
been analyzed every few years to estimate northern spotted owl 
population trends (Anderson and Burnham 1992; Burnham et al. 1994; 
Franklin et al. 1999; Anthony et al. 2006). The most current evaluation 
of population status and trends is based on data through 2003 (Anthony 
et al. 2006). Based on this analysis, populations on 8 of 12 study 
areas (Wenatchee, Cle Elum, Rainier, Olympic Peninsula, Oregon Coast 
Ranges, Warm Springs, H.J. Andrews, and Simpson) were declining 
(Anthony et al. 2006, p. 23). Estimates of realized population change 
(cumulative population change across all study years) indicated that, 
in the more rapidly declining populations (Wenatchee, Cle Elum, 
Rainier, and Warm Springs), the 2003 populations were 50 to 70 percent 
of the population sizes observed in 1994 or 1995 (Anthony et al. 2006, 
pp. 25 to 26). Populations in the remaining four study areas (Tyee, 
Klamath, South Oregon Cascades, and Hoopa) appear to have remained 
stable through 2003 (Anthony et al. 2006, p. 25). A meta-analysis 
combining data from all 12 study areas indicates that rangewide the 
population declined at a rate of about 3.7 percent per year from 1985 
to 2003. Northern spotted owl populations on Federal lands had better 
demographic rates than elsewhere, but still declined at a mean annual 
rate of about 2.4 percent (Anthony et al. 2006, pp. 33 to 34).
    The barred owl (Strix varia) has recently 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), survival 
(Anthony et al. 2006), and number of territories occupied (Kelly et al. 
2003, p. 51; Olson et al. 2005). 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 likely to be undetected by standard survey 
methods (Olson et al. 2005; Crozier et al. 2006). It is therefore 
difficult to determine whether northern spotted owls no longer occupy a 
site, or whether they may still be present but are not detected. The 
2007 Draft Recovery Plan for the Northern Spotted owl concludes that 
``barred owls are exacerbating the spotted owl population decline, 
particularly in Washington, portions of Oregon, and the northern coast 
of California'' (USFWS 2007, p. 126).
    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 current 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).
Life History and Ecology
    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 to 24; 
Solis and Guti[eacute]rrez 1990, p. 742; Forsman et al. 2005, p. 374). 
Pairs are non-migratory and remain on their home range throughout the 
year, though 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 1995a, p. 649; but see Rosenberg et 
al. 1994, pp. 1512 to 1515). The northern spotted owl shows strong 
year-round fidelity to its breeding site, even when not nesting (Solis 
1983, pp. 23 to 28; Forsman et al. 1984, pp. 52 to 53) or after natural 
disturbance alters habitat characteristics within the home range (Bond 
et al. 2002, pp. 1024 to 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 (Carey and Peeler 1995, p. 236) 
in which natal dispersal and survival to reproductive age are the most 
vulnerable stages. 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 blocks limits the potentially adverse genetic effects of 
inbreeding and provides demographic support to declining populations 
(Thomas et al. 1990, pp. 271 to 272). A discussion of northern spotted 
owl dispersal is included in the Primary Constituent Elements section 
of this proposed rule.
Prey
    Northern spotted owls forage primarily on arboreal and semi-
arboreal mammals (summarized in Courtney et al. 2004, pp. 4-31 to 4-
32). The primary prey species utilized depends on geographic area, but 
may include northern flying squirrels (Glaucomys sabrinus), two species 
of woodrats (Neotoma spp.), two species of red-backed voles 
(Clethrionomys spp.), red tree voles (Arborimus longicaudus), two 
species of deer mice (Peromyscus spp.), and two species of lagomorphs 
(rabbits and hares) (Courtney et al. 2004, p. 4-5). 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), although the use of these prey species is more 
seasonal (mainly spring, summer, and early fall) (Forsman et al. 2001, 
p. 146; Forsman et al. 2004, p. 223).
    There is a clear geographic pattern to the northern spotted owl 
diet that varies with distribution and abundance of prey and habitat 
type (Thomas et al. 1990, p.

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201; Forsman et al. 2001, p. 146; Courtney et al. 2004, p. 4-7). 
Northern flying squirrels are the dominant prey species in the northern 
Western Hemlock/Douglas-fir forests. Dusky-footed woodrats (Neotoma 
fuscipes) are more important in the southern drier, mixed-conifer/
mixed-evergreen forests. Both prey species are co-dominant through the 
southwest interior of Oregon (Courtney et al. 2004, pp. 4-7 to 4-8).
    Northern flying squirrels are nocturnal arboreal rodents and the 
primary prey of northern spotted owls in the northern provinces. 
Forests that support northern flying squirrels provide den sites, 
usually cavities in large snags, but northern flying squirrels 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 1995b, 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. 3-12). Northern flying squirrel densities tend to be higher 
in older forest stands with ericaceous shrubs (e.g., rhododendron) and 
an abundance of large snags (Carey 1995b, p. 654), likely because these 
older forests produce a higher forage biomass. Flying squirrel density 
tends to increase with stand age (Carey 1995b, pp. 653 to 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 to 591). The main factors that may limit northern flying squirrel 
densities are the availability of den structures and food, especially 
hypogeous fungi (Gomez et al. 2005, pp. 1677 to 1678).
    For northern spotted owls in northern California, southwestern 
Oregon, and the Willamette Valley, dusky-footed woodrats constitute the 
primary prey (Carey et al. 1999, p. 65). Habitats that support dusky-
footed woodrats usually include early seral mixed-conifer/mixed 
evergreen forests close to water (Carey et al. 1999, p. 77). Dusky-
footed woodrats reach high densities in both old forests with openings 
and closed-canopy young forests (Sakai and Noon 1993, pp. 376 to 378; 
Carey et al. 1999, p. 73), and use hardwood stands in mixed evergreen 
forests (Carey et al. 1999, p. 73). 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 
dusky-footed woodrats. The main factors that may limit dusky-footed 
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).
Home Range, Forest Condition, Survival, and Reproduction
    Territorial northern spotted owls remain resident on their home 
range throughout the year, therefore, these home ranges must provide 
all of the habitat components needed for the survival and successful 
reproduction of a pair of owls. The home range is composed of a core 
area, the area of most intensive use and nesting, and the remainder of 
the home range which is utilized for additional foraging and roosting. 
In nearly all studies of northern spotted owl nesting habitat, the 
amount of mature and old-growth forest was greater within northern 
spotted owl sites than at random sites at the home range and core area 
scale (Courtney et al. 2004, pp. 5-6, 5-13), and forests were less 
fragmented (Hunter et al. 1995, p. 688). The amount of quality 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 to 156; Dugger et 
al. 2005, p. 871). A more complete description of the home range is 
presented in the Primary Constituent Elements section of this proposed 
rule.
    The size, configuration, and characteristics of vegetation patches 
within core areas 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 non-
forested areas in their home range (Olson et al. 2004, pp. 1049 to 
1050), a pattern similar to that found in the California Klamath 
Province. In contrast, studies conducted in the Oregon Cascades found 
that habitat characteristics were not good predictors of northern 
spotted owl survival or reproduction (Anthony et al. 2002, p. 49). 
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, core areas composed predominantly 
of old forest may not be optimal for northern spotted owls in the 
California Klamath Province and Oregon Coast Ranges Province.
Habitat Use
    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 (Lint 2005; Buchanan 
2004; Forsman et al. 2005; Zabel et al. 2003; Irwin et al. 2000) 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 
essential features of suitable habitat for the northern spotted owl. 
Detailed characterizations of each of these functional habitat types 
and their relative distribution are described in the Primary 
Constituent Elements section of this proposed rule.

Summary of Conservation Strategies for the Northern Spotted Owl

    Prior and subsequent to the listing of the northern spotted owl (FR 
55 26175), many committees, task forces, and work groups were formed to 
find biologically and socially acceptable solutions to the dilemma of 
halting its decline (Meslow 1993, entire document), commencing in 1982 
with the development of a regional guide for management of the northern 
spotted owl (Courtney et al. 2004, p. 9-3). Today, northern spotted owl 
conservation on Federal lands within the range of the northern spotted 
owl in Washington, Oregon, and California is largely accomplished 
through the Forest Service's Land and Resource Management Plans (LRMP) 
and Bureau of Land Management's (BLM) Resource Management Plans (RMP), 
as amended by the Record of Decision for Amendments to Forest Service 
and BLM Planning Documents within the Range of the Northern Spotted Owl 
(USDA and USDI 1994a, p. 31; USDA and USDI 1994b). The LRMPs/RMPs were 
considered to be, in part, the Federal contribution to recovery for the 
northern spotted owl (USDA and USDI 1994a, Appendix G). The work of the

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Interagency Scientific Committee to Address Conservation of the 
Northern Spotted Owl (ISC) in 1990 and its resulting core strategies 
has served as the foundation for subsequent conservation planning, 
including the 1992 Final Draft Recovery Plan for the Northern Spotted 
Owl (Courtney et al. 2004, p. 9-3), the original designation of 
critical habitat for the northern spotted owl (57 FR 1796; January 15, 
1992), and the 2007 Draft Recovery Plan for the Northern Spotted Owl 
(USFWS 2007).

Interagency Scientific Committee (ISC)--1990

    The Interagency Scientific Committee (ISC), was chartered in 1989 
by four Federal agencies, the U.S. Department of Agriculture's Forest 
Service (FS) and U.S. Department of the Interior's Bureau of Land 
Management (BLM), Fish and Wildlife Service, and National Park Service, 
to develop a scientific conservation strategy for the northern spotted 
owl (Thomas et al. 1990). In 1992, the Forest Service formally adopted 
the ISC Conservation Strategy for the Northern Spotted Owl as a basis 
for its planned management. However, for a variety of reasons, the plan 
was never implemented (Courtney et al. 2004, p. 9-4).
    The ISC's Conservation Strategy was built on a foundation of five 
conservation biology principles. In general, the ISC favors the 
protection of large blocks of habitat capable of supporting multiple 
pairs of northern spotted owls spaced closely enough to facilitate 
dispersal between the blocks. The results of applying these principles 
were of key importance to the development of this revised critical 
habitat proposal, and are summarized below:
    (1) Large Block Size. The ISC strategy emphasizes the importance of 
managing large and well-distributed blocks of northern spotted owl 
habitat, called Habitat Conservation Areas (HCAs), which are 
sufficiently connected to maintain a stable and well-distributed 
population throughout the northern spotted owl's range. The target 
population for HCAs was derived from empirical data and modeling 
results supporting the conclusion that clusters of 20 pairs of northern 
spotted owls should be stable over the long term, given the rates of 
dispersal among them by juveniles (Thomas et al. 1990, pp. 24, App. O). 
At the time of selection, some HCAs contained sufficient habitat and 
resident northern spotted owls to meet or exceed the 20-pair target, 
while others were deficient in both habitat and pairs. The ISC 
anticipated that northern spotted owl habitat, and therefore the target 
number of pairs, would be recruited over time (Thomas et al. 1990, p. 
23). Large block size was determined based on the target number of 
northern spotted owl pairs and the median provincial home range size of 
pairs. Based on habitat use studies, the median home range used was 
larger in the north (14,271 ac (5,775 ha)) and smaller in the south 
(2,955 ac (1,196 ha)) (Thomas et al. 1990, App. I). Overall, the large 
habitat blocks are considered sufficiently large so that they can 
remain stable over the long run, with low to moderate dispersal from 
adjacent blocks (Thomas et al. 1990, p. 24).
    In areas where the actual habitat conditions, future capability of 
lands to develop into northern spotted owl habitat, and northern 
spotted owl densities did not allow for the large block approach, 
smaller habitat blocks were identified in strategic locations (Thomas 
et al. 1990, p. 28). The ISC recognized that the northern spotted owl 
populations in these smaller blocks were relatively less stable, but 
would still contribute to the metapopulation structure across the 
subspecies' range (Thomas et al. 1990, pp. 27 to 30, 308). The term 
metapopulation refers to a set of local populations linked by 
dispersing individuals. The ISC adopted a metapopulation approach to 
management as an attempt to provide the northern spotted owl with 
habitat distributed across the landscape in a fashion most similar to 
the historical configuration, given existing patterns of fragmentation. 
This approach was considered the best hedge against future extinction 
(Thomas et al. 1990, p. 23).
    (2) Distance Between Habitat Blocks. The success of a northern 
spotted owl conservation strategy based on metapopulation structure 
depends, in part, on dispersal between habitat blocks. Therefore, the 
ISC developed habitat blocks separated by distances well within the 
known dispersal range of juveniles (Thomas et al. 1990, p. 307). For 
the northern spotted owl, the ISC indicates that the distance between 
large habitat blocks should be within the known median dispersal 
distances of at least two-thirds of all juveniles. This translated into 
a maximum allowable distance of 12 mi (19.3 km) between the nearest 
points of contact of neighboring large habitat blocks (Thomas et al. 
1990, p. 307, Table P1).
    Populations in small habitat blocks are inherently less stable and 
more prone to local extinctions than those in large blocks and are 
therefore more reliant on immigration from neighboring blocks to remain 
extant (Thomas et al. 1990, pp. 262, 266, 308). To provide an 
additional measure of population security for the small habitat blocks, 
the ISC set a shorter distance of 7 mi (11.2 km) to the adjacent 
blocks. This was less than the median dispersal distance estimate from 
banded northern spotted owls, and is within the dispersal range of more 
than 75 percent of all radio-marked juveniles (Thomas et al. 1990, p. 
308). This shorter distance was intended to improve the likelihood of 
successful dispersal from adjacent blocks, thereby reducing the 
potential for local extinctions within small habitat blocks (Thomas et 
al. 1990, p. 308).
    (3) Rangewide Distribution. A primary reason for designating 
habitat blocks throughout the northern spotted owl's range was to 
ensure that stochastic events such as large fires or windstorms that 
may occur in a portion of the range would not negatively impact the 
entire population (Thomas et al. 1990, p. 294). The ISC's rangewide 
distribution of large habitat blocks offered some resiliency to 
maintain the subspecies and habitat variation across provinces and 
offered some protection against stressors such as stochastic events 
(e.g., large fires). This conservation principle provides a hedge 
against extinction of the northern spotted owl due to either small or 
large catastrophic events. In addition, large, well-distributed blocks 
of unfragmented habitat may assist the northern spotted owl in 
responding to the barred owl, which has recently expanded its range and 
now overlaps with the range of the northern spotted owl (Herter and 
Hicks 2000, p. 284).
    (4) Contiguous Habitat. The ISC Strategy states that the less 
fragmented the habitat within blocks is, the better habitat will 
function for northern spotted owls. Habitat fragmentation may cause 
habitat deterioration from edge effects, increased risk of predation, 
and potential displacement by barred owls (Thomas et al. 1990, p. 22 to 
23). At the time, information such as that provided by the more recent 
studies in the California Klamath and Oregon Coast Range provinces 
regarding the potential benefits of heterogeneity and forest edge in 
these areas (Franklin et al. 2000, Olson et al. 2004) was not known.
    (5) Dispersal Habitat. Stability of the northern spotted owl 
population under the ISC Conservation Strategy is dependent on the 
movement of individuals among habitat blocks for population support 
(Thomas et al. 1990, p. 26). To facilitate the movement of northern 
spotted owls between blocks, the ISC requires intervening forest lands 
to be managed in a manner that will support dispersing northern spotted 
owls (Thomas et al. 1990, p. 326 to 327).

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Designation of Critical Habitat--1992

    The original designation of critical habitat for the northern 
spotted owl was finalized in 1992 (57 FR 1796; January 15, 1992). 
Critical habitat was identified based on the conservation principles 
set forth in the ISC Conservation Strategy for the Northern Spotted Owl 
(Thomas et al. 1990), including the development and maintenance of 
large contiguous blocks of habitat to support multiple reproducing 
pairs of owls; minimizing fragmentation and edge effect to improve 
habitat quality; minimizing distance between blocks to facilitate 
dispersal; and maintaining rangewide distribution of habitat to 
facilitate recovery (57 FR 1803-1804; January 15, 1992). The emphasis 
on large, continuous blocks of habitat relied on the ISC's 
identification of HCAs as a starting point (Thomas et al. 1990; p. 
315). Category 1 HCAs were those with the potential to support 20 or 
more pairs, and category 2 HCAs were those with the potential to 
support fewer than 20 pairs. Although the ISC had also identified 
category 3 HCAs, areas capable of supporting only a single pair of 
owls, the critical habitat concentrated on areas of sufficient size to 
support at least two pairs. The final critical habitat designation 
included 6,887,000 ac (2,787,070 ha) of Federal lands within the range 
of the northern spotted owl. Of those acres, approximately 5,700,000 ac 
(2,317,073 ha) were within the HCA system proposed by the ISC, and an 
additional 1,887,000 ac (767,073 ha) were designated as a measure to 
further enhance the HCAs already identified (57 FR 1804-1805; January 
15, 1992).

Northern Spotted Owl Final Draft Recovery Plan--1992

    The Department of the Interior began development of a recovery plan 
for the northern spotted owl in 1990. After reviewing a number of 
conservation strategies, the 1992 Recovery Team settled on the ISC 
reserve design (i.e., size and spacing of habitat blocks) as a basis 
for the 1992 Final Draft Northern Spotted Owl Recovery Plan (USDI 1992, 
p. 357). HCAs were renamed Designated Conservation Areas (DCAs), but 
the category designations remained the same (i.e., a category 1 DCA was 
designed to support at least 20 pairs of northern spotted owls, and a 
category 2 DCA supports from 2 to 19 pairs). The 1992 Recovery Team's 
objective in remapping the HCAs was to provide a level of habitat 
protection in the DCAs that was at least equal to that provided by 
HCAs, while increasing the biological and economic efficiency of the 
network. The fundamental sizing and spacing criteria from Thomas et al. 
(1990) were applied during mapping of the DCAs. The overall structural 
elements developed by the ISC remained, although the draft recovery 
plan was never finalized.

Forest Ecosystem Management Assessment Team--1993

    The Forest Ecosystem Management Assessment Team (FEMAT) (USDA et 
al. 1993) was created to provide a review of scientific issues and 
options for a regional plan to manage Federal forests. The primary 
concepts of the FEMAT Option 9 were adopted through the Record of 
Decision for Amendments to Forest Service and BLM Planning Documents 
within the Range of the Northern Spotted Owl, signed in 1994, and 
amended the Forest Service LRMPs and BLM RMPs within the range of the 
northern spotted owl relative to the management of habitat for late-
successional and old-growth forest species (USDA and USDI 1994b). The 
principal components that contribute to conserving the northern spotted 
owl include the concepts of large reserve blocks of habitat (managed 
for forests resembling northern spotted owl habitat), connectivity, and 
silviculture treatments to accelerate habitat development, all of which 
were founded on the ISC concepts (Courtney et al. 2004, 9-7).
    The LRMPs/RMPs include a network of reserve allocations called 
Late-Successional Reserves (LSRs) designed, in part, to support 
clusters of reproducing northern spotted owl pairs across the range of 
the subspecies. It should be noted that LSRs are managed to meet the 
need of multiple species that depend on late-successional forests, and 
are not exclusive to management for northern spotted owls. Therefore 
although many LSRs benefit northern spotted owls, not all LSRs 
necessarily represent optimal habitat for northern spotted owls since 
they are intended to provide for other species as well.
    Silvicultural treatment of young forest (less than 80 years of age) 
is allowed within LSRs for the purpose of accelerating the development 
of late-successional habitat. This provision was included because the 
LSRs initially included a significant amount of area that had been 
logged and were in young, plantation-style forests. Because the 
development of large contiguous, unfragmented, blocks of late-
successional forest was a key element of the ISC's strategy, activities 
designed to accelerate restoration of simplified young stands were 
viewed as appropriate.
    The LRMPs/RMPs allow for silvicultural treatments of older forests 
in LSRs on sites characterized by frequent, light to moderate intensity 
fire, such as pine and mixed-conifer dominated forests on the eastern 
slopes of the Cascade Range and in the Siskiyou-Klamath region. This 
provision was included because of the potential for 
uncharacteristically intense wildfire on sites where higher than normal 
amounts of fuel have accumulated. Such fires pose a high risk of 
temporary or even long-term loss of old-growth conditions, including 
northern spotted owl habitat, and treatments may help reduce this risk.

2006/2007 Recovery Planning Process for the Northern Spotted Owl

    In April 2006, the Service convened an interdisciplinary Northern 
Spotted Owl Recovery Team to incorporate the most recent scientific 
information into a current recovery plan for the species. The Recovery 
Team sought input from northern spotted owl experts on the main threats 
to the rangewide northern spotted owl population: competition from 
barred owls, loss of habitat amount and distribution from past 
activities and disturbances, and ongoing habitat loss to timber 
harvest. The Draft Recovery Plan for the Northern Spotted Owl (USFWS 
2007) provides two options to address the threats posed by habitat loss 
and modification. Both options are based on the same underlying 
science, much of which is from the ISC (Thomas et al. 1990). Option 1 
maps the specific conservation area boundaries where most of the 
recovery actions and criteria will be targeted. These conservation 
areas are called Managed Owl Conservation Areas, or MOCAs, and are 
mapped in the 2007 Draft Recovery Plan (USFWS 2007). Option 2 of the 
2007 Draft Recovery Plan provides a rule set that defines the size and 
distance of the conservation areas needed for recovery, while 
recognizing that the habitat demands of the northern spotted owl vary 
across its range. The rule set is designed to help guide the Federal 
land management agencies when undertaking conservation actions for the 
northern spotted owl.
    The network of habitat blocks stemming from both options is based 
on the conservation biology strategies of the ISC (Thomas et al. 1990, 
p. 23) and provides the basis for this proposed revised critical 
habitat designation. The 2007 Draft Recovery Plan suggests that the 
recovery of the northern spotted owl can be achieved by managing for 
appropriate habitat on Federal lands within the range of the northern 
spotted owl in the United States, drawing on

[[Page 32455]]

voluntary recovery measures on intervening non-Federal lands. 
Conservation contributions by private, State, and other landowners in 
areas between or adjacent to habitat blocks are expected to increase 
the likelihood of northern spotted owl recovery. Consistent with the 
1992 designation, we have identified only Federal lands as proposed 
revised critical habitat for the northern spotted owl.

Previous Federal Actions

    A description of previous Federal actions up to the time of listing 
on June 26, 1990, can be found in the final rule listing the northern 
spotted owl (55 FR 26114). On January 15, 1992, we published the final 
rule designating critical habitat for the northern spotted owl (57 FR 
1796). In December 1992, we completed the Final Draft Recovery Plan for 
the Northern Spotted Owl in Washington, Oregon, and California (USDI 
1992).
    On April 21, 2003, we published a notice of review initiating a 5-
year review of the northern spotted owl (68 FR 19569). We then 
published a second information request for the 5-year review on July 
25, 2003 (68 FR 44093). We contracted a comprehensive status review of 
the northern spotted owl to provide the best available scientific 
information for the 5-year review. The status review report was 
completed in September 2004 and continues to serve as the most current 
comprehensive summary of scientific information on the northern spotted 
owl (Courtney et al. 2004). 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.
    On January 13, 2003, we entered into a settlement agreement with 
the American Forest Resource Council, Western Council of Industrial 
Workers, Swanson Group Inc., and Rough & Ready Lumber Company to 
conduct a rulemaking to consider potential revisions to critical 
habitat for the northern spotted owl that includes a revised 
consideration of economic impacts and any other relevant aspects of 
designation. The dates for completion of this review have been extended 
and currently call for the Service to submit a proposed revised 
critical habitat designation to the Federal Register by June 1, 2007, 
and to submit a final revised critical habitat designation to the 
Federal Register by June 1, 2008.

Critical Habitat

    Critical habitat is defined in section 3 of the Act as: (i) The 
specific areas within the geographical area occupied by a species, at 
the time it is listed in accordance with the Act, on which are found 
those physical or biological features (I) essential to the conservation 
of the species and (II) that may require special management 
considerations or protection; and (ii) specific areas outside the 
geographical area occupied by a 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 all methods and procedures necessary to bring any endangered 
species 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 prohibition against destruction or adverse modification of 
critical habitat with regard to actions carried out, funded, or 
authorized by a Federal agency. Section 7 requires consultation on 
Federal actions that are likely to result in effects to 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 government or 
public access to private lands. Section 7 is a purely protective 
measure and does not require implementation of restoration, recovery, 
or enhancement measures.
    To be included in a critical habitat designation, the habitat 
within the area occupied by the species must first have features that 
are essential to the conservation of the species. Critical habitat 
designations identify, to the extent known using the best scientific 
data available, habitat areas that provide essential life cycle needs 
of the species (i.e., areas on which are found the primary constituent 
elements, as defined at 50 CFR 424.12(b)).
    Habitat occupied at the time of listing may be included in critical 
habitat only if its essential features may require special management 
or protection. An area currently occupied by the species but not known 
to be occupied at the time of listing will likely, but not always, be 
essential to the conservation of the species and, therefore, typically 
included in the critical habitat designation. When the best available 
scientific data do not demonstrate that the conservation needs of the 
species require additional areas, we will not designate critical 
habitat in areas outside the geographical area occupied by the species 
at the time of listing.
    The Service's Policy on Information Standards Under the Endangered 
Species Act, published in the Federal Register on July 1, 1994 (59 FR 
34271), and section 515 of the Treasury and General Government 
Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658) 
and the associated Information Quality Guidelines issued by the 
Service, provide criteria, establish procedures, and provide guidance 
to ensure that decisions made by the Service represent the best 
scientific data available. They require Service 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 
determining which areas are eligible for consideration as critical 
habitat, a primary source of information is generally the listing 
package for the species. Additional information sources 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, or other unpublished 
materials and expert opinion or personal knowledge. All information is 
used in accordance with the provisions of section 515 of the Treasury 
and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 
106-554; H.R. 5658) and the associated Information Quality Guidelines 
issued by the Service.
    Section 4 of the Act requires that we designate critical habitat on 
the basis of the best scientific data available. Habitat is often 
dynamic, and species may move from one area to another over time. 
Furthermore, we recognize that designation of critical habitat may not 
include all of the habitat areas that may eventually be determined to 
be necessary for the recovery of the species. For these reasons, 
critical habitat designations do not signal that habitat outside the 
designation is unimportant or may not be required for recovery.
    Areas that support populations, but are outside the critical 
habitat designation, will continue to be subject to conservation 
actions implemented under section 7(a)(1) of the Act and to the 
regulatory protections afforded by

[[Page 32456]]

the section 7(a)(2) jeopardy standard, as determined on the basis of 
the best available information at the time of the action. Federally 
funded or permitted projects affecting listed species outside their 
designated critical habitat areas may still result in jeopardy findings 
in some cases. 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, or other species conservation planning 
efforts if new information available to these planning efforts calls 
for a different outcome.

Methods

    As required by section 4(b)(2) of the Act, we use the best 
scientific data available in determining areas that contain the 
features that are essential to the conservation of the northern spotted 
owl. For this critical habitat revision, we relied upon a variety of 
information sources to identify those areas, as well as to assess the 
habitat requirements of the species, including the 2007 Draft Recovery 
Plan for the Northern Spotted Owl (USFWS 2007), the 2004 Status Review 
for the Northern Spotted Owl (Courtney et al. 2004), the Northern 
Spotted Owl 5-year Review (USFWS 2004), the Final Supplemental 
Environmental Impact Statement and Record of Decision for Amendments to 
Forest Service and BLM Planning Documents within the Range of the 
Northern Spotted Owl (USDA and USDI 1994 a, b), the 1992 final critical 
habitat designation (57 FR 1796; January 15, 1992), Interagency 
Scientific Committee Conservation Strategy for the Northern Spotted Owl 
(Thomas et al. 1990), and GIS data layers, including those for northern 
spotted owl habitat, Federal land use allocations, land ownership, and 
northern spotted owl occupancy data. This proposed rule only addresses 
revisions to the current designation. For discussion of the methods 
used for the existing designation, please refer to that final 
designation (57 FR 1796; January 15, 1992).

Primary Constituent Elements

    In accordance with section 3(5)(A)(i) of the Act and regulations at 
50 CFR 424.12, in determining which areas to propose as critical 
habitat, we consider physical and biological features (primary 
constituent elements, or PCEs) that are essential to the conservation 
of the species, and within the area occupied by the species at the time 
of listing, that may require special management considerations and 
protection. These include, but are not limited to, space for individual 
and population growth and for normal behavior; food, water, air, light, 
minerals, or other nutritional or physiological requirements; cover or 
shelter; sites for breeding, reproduction, and rearing (or development) 
of offspring; and habitats that are protected from disturbance or are 
representative of the historic geographical and ecological 
distributions of a species.
    The specific primary constituent elements required for the northern 
spotted owl are derived from the biological needs of the species as 
described in the Background section of this proposal and the following 
information.

Space for Population Growth and for Normal Behavior

    Northern spotted owls remain on their home range throughout the 
year therefore this area must provide all the habitat components and 
prey needed to provide for the survival and successful reproduction of 
a territorial pair. The home range of a northern spotted owl is 
relatively large and varies in size among and within provinces, 
generally increasing to the north (Courtney et al. 2004, p. 5-24; 55 FR 
25117) where home range size ranges from 2,955 ac (1,196 ha) in the 
Oregon Cascades (Thomas et al. 1990, p. 194) to 14,271 ac (5,775 ha) on 
the Olympic Peninsula (USDI 1992, p. 23; USFWS 1994 in litt., p. 1). 
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 Guti?rrez 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).
    Northern spotted owl home ranges contain two distinct use areas: 
the core area, which is the area that is used most intensively and 
usually includes the nesting area (Bingham and Noon 1997, pp. 134 to 
135), and the remainder of the home range which is used for foraging 
and roosting. The size of core areas varies considerably across the 
subspecies? geographic 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 to 10, Table 2; Zabel et al. 2003, pp. 1036 to 1038).
    Core areas contain greater proportions of mature/old forest than 
random or non-use areas (Courtney et al. 2004, p. 5-13), and the 
quality of 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 nesting, roosting, and foraging functions (Carey and Peeler 
1995, pp. 233 to 236; Rosenberg and McKelvey 1999, pp. 1035 to 1037).
    The primary function of the remainder of the home range outside the 
core area is to provide subsidiary roosting and foraging opportunities 
for the resident pair that are essential to the year-round survival of 
the resident pair if they partially deplete the prey populations in the 
core area.

Sites for Breeding, Reproduction, and Rearing of Offspring (Nesting)

    Nesting habitat provides structural features for nesting, 
protection from adverse weather conditions, and cover to reduce 
predation risks for adults and young. Nesting stands typically include 
a moderate to high canopy closure (60 to 80 percent); a multi-layered, 
multi-species canopy with large (greater than 30 inches (in) (76 
centimeters (cm)) diameter at breast height (dbh)) overstory trees; a 
high incidence of large trees with various deformities (e.g., large 
cavities, broken tops, mistletoe infections, and other evidence of 
decadence); large snags; large accumulations of fallen trees and other 
woody debris on the ground; and sufficient open space below the canopy 
for northern spotted owls to fly (Thomas et al. 1990, p. 164; 57 FR 
1798).
    Recent studies found that northern spotted owl nest stands tend to 
have greater tree basal area, number of canopy layers, density of 
broken-top trees, number or basal area of decadent snags, and volume of 
decadent logs (Courtney et al. 2004, pp. 5-16 to 5-19, 5-23). In some 
forest types, northern

[[Page 32457]]

spotted owls nest in younger forest stands that contain structural 
characteristics of older forests. Nesting northern spotted owls 
consistently occupy stands having high canopy cover that may provide 
thermoregulatory benefits (Weathers et al. 2001, p. 686), allowing 
northern spotted owls a wider range of choices for locating thermally-
neutral roosts near the nest site. High canopy closure may also conceal 
northern spotted owls, reducing potential predation.
    To support northern spotted owl reproduction, a home range requires 
appropriate amounts of nesting, roosting, and foraging habitat arrayed 
so that nesting pairs can use it efficiently and safely. In the 
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 portions of the range in the south, 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 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. The appropriate amount and spatial distribution of 
nesting habitat is essential for successful reproduction of northern 
spotted owls.

Cover or Shelter (Roosting)

    The primary functions of roosting habitat are to facilitate 
thermoregulation in summer or winter, shelter northern spotted owls 
from precipitation, and provide cover to reduce predation risk while 
resting or foraging. Studies of roosting locations found that northern 
spotted owls tended to use stands with greater vertical canopy layering 
(Mills et al. 1993, pp. 318 to 319), canopy closure (King 1993, p. 45), 
snag diameter (Mills et al. 1993, pp. 318 to 319), diameter of large 
trees (Herter et al. 2002, pp. 437, 441), and amounts of large woody 
debris (Chow 2001, p. 24; reviewed in Courtney et al. 2004, pp. 5-14 to 
4-16, 5-23). The characteristics of roosting habitat differ from those 
of nesting habitat only in that roosting habitat need not contain the 
specific structural features used for nesting (Thomas et al. 1990, p. 
62).

Food or Other Nutritional or Physiological Requirements (Foraging)

    The primary function of foraging habitat is to provide a food 
supply for survival and reproduction. Foraging activity is positively 
associated with tree height diversity (North et al. 1999, p. 524), 
canopy closure (Irwin et al. 2000, p. 180; Courtney et al. 2004, p. 5-
15), snag volume, density of snags greater than 20 in (50 cm) dbh 
(North et al. 1999, p. 524; Irwin et al. 2000, pp. 179 to 180; Courtney 
et al. 2004, p. 5-15), density of trees greater than or equal to 31 in 
(80 cm) dbh (North et al. 1999, p. 524), volume of woody debris (Irwin 
et al. 2000, pp. 179 to 80), and young forests with some structural 
characteristics of old forests (Carey et al. 1992, pp. 245 to 247; 
Irwin et al. 2000, pp. 178 to 179). Northern spotted owls select old 
forests for foraging in greater proportion than its availability at the 
landscape scale (Carey et al. 1992, pp. 236 to 237; Carey and Peeler 
1995, p. 235; Forsman et al. 2005, pp. 372 to 373), but will forage in 
younger stands with high prey densities and access to prey (Carey et 
al. 1992, p. 247; Rosenberg and Anthony 1992, p. 165; Thome et al. 
1999, pp. 56 to 57).
    Because northern spotted owls show a clear geographic 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 structure that support northern flying squirrels 
(Rosenberg and Anthony 1992, p. 165; Carey et al. 1992, p. 233). 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 to 90; Sakai and Noon 1993, pp. 
376 to 378; Carey et al. 1999, p. 73; Sakai and Noon 1997, p. 347; 
Franklin et al. 2000, p. 579). An adequate amount and distribution of 
foraging habitat within the home range is essential to the survival and 
reproduction of northern spotted owls.

Habitats That Are Representative of the Historical Geographical and 
Ecological Distributions of the Northern Spotted Owl

    The northern spotted owl inhabits most of the major types of 
coniferous forests across its geographic 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; Franklin and Dyrness 
1988; Thomas et al. 1990). Vegetative composition of northern spotted 
owl habitat changes from north to south and from west to east within 
the subspecies' range. The lower elevation limit of subalpine 
vegetation types defines the uppermost elevation used by northern 
spotted owls. This elevation varies with latitude from about 3,000 feet 
(ft) (914 meters (m)) above sea level near the northern edge of the 
range to about 6,000 ft (1,828 m) above sea level at the southern edge 
(Lint 2005, p. 32).
    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. In the Klamath Mountains 
Provinces in 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 (Lint 2005, pp. 31 to 33).

Conditions Supporting Non-Resident Owls

    Landscapes with northern spotted owl habitat likely contain non-
resident (non-breeding) northern spotted owls, sometimes referred to as 
``floaters'' (Forsman et al. 2002, pp. 15, 26). These habitats 
contribute to stable or increasing populations of northern spotted owls 
by maintaining sufficient individuals to quickly fill territorial 
vacancies when residents die or leave their territories. Where large 
blocks of habitat with multiple breeding pairs occur, the opportunities 
for this integration are enhanced due to the within-block production of 
potential replacement birds (Thomas et al. 1990, p. 295, 307).
    Intervening habitats are important in supporting the successful 
dispersal of northern spotted owls that is essential to maintaining the 
genetic and demographic connection among populations both within and 
across

[[Page 32458]]

provinces. Habitats that support movements between larger blocks 
providing nesting, roosting, and foraging habitats for northern spotted 
owls act to limit the adverse genetic effects of inbreeding and provide 
demographic support to declining populations (Thomas et al. 1990, pp. 
271 to 272). Dispersing juvenile northern spotted owls experience high 
mortality rates (more than 70 percent in some studies (Miller 1989, pp. 
32 to 41; Franklin et al. 1999, pp. 25, 28; 55 FR 26115)) from 
starvation, predation, and accidents (Miller 1989, pp. 41 to 44; 
Forsman et al. 2002, pp. 18 to 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.
    Juvenile dispersal occurs in steps (Forsman et al. 2002, pp. 13 to 
14) between which dispersing juveniles settle into temporary home 
ranges for up to several months (Forsman et al. 2002, p. 13). 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).
    Successful juvenile dispersal may depend on locating unoccupied 
suitable habitat in close proximity to other occupied sites (LaHaye et 
al. 2001, pp. 697 to 698). 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). Approximately 68 percent of radio-marked juveniles 
of both sexes dispersed greater than 12 mi (19 km) from their natal 
areas, which was also the average dispersal distance. Approximately 80 
percent dispersed greater than 7 mi (11 km) from their natal areas 
(Thomas et al. 1990, pp. 305 to 306). Northern spotted owls regularly 
disperse through highly fragmented forested landscapes that are typical 
of the mountain ranges in western Washington and Oregon (Forsman et al. 
2002, p. 22), 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.

Primary Constituent Elements for the Northern Spotted Owl

    Under our regulations, we are required to identify the known 
physical and biological features (PCEs) essential to the conservation 
of the northern spotted owl. All areas proposed as revised critical 
habitat for the northern spotted owl are within the geographic area 
occupied by the species and contain sufficient PCEs to support at least 
one life history function. Much of the recent research on northern 
spotted owl biology supports the PCEs described in the previous 
critical habitat designation; based on our current knowledge, the PCEs 
described here are more detailed and specific, where possible. Based on 
our current knowledge of the life history, biology, and ecology of the 
species and the requirements of the habitat to sustain the essential 
life history functions of the species, we have determined that the 
northern spotted owl's PCEs are:
    (1) Forest types known to support the northern spotted owl across 
its geographic range. These forest types include Sitka spruce, western 
hemlock, mixed conifer and mixed evergreen, grand fir, Pacific silver 
fir, Douglas-fir, white fir, Shasta red fir, redwood/Douglas-fir (in 
coastal California and southwestern Oregon), and the moist end of the 
p