[Federal Register: February 14, 2003 (Volume 68, Number 31)]
[Page 7580-7608]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]



Fish and Wildlife Service

Endangered and Threatened Wildlife and Plants; 12-Month Finding 
for a Petition To List the California Spotted Owl (Strix occidentalis 

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.


SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding for a petition to list the California spotted owl 
(Strix occidentalis occidentalis) under the Endangered Species Act of 
1973, as amended. After reviewing the best available scientific and 
commercial information available, we find that the petitioned action is 
not warranted. We continue to ask the public to submit to us any new 
information that becomes available concerning the status of or threats 
to this species. This information will help us monitor and encourage 
the conservation of this species.

DATES: The finding announced in this document was made on February 7, 
2003. You may submit new information concerning these species for our 
consideration at any time.

ADDRESSES: You may send data, information, comments, or questions 
concerning this finding to Field Supervisor (Attn: CASPO), Sacramento 
Fish and Wildlife Office, U.S. Fish and Wildlife Service, 2800 Cottage 
Way, Room W-2605, Sacramento, California 95825. You may inspect the 
petition, administrative finding, supporting information, and comments 
received, by appointment, during normal business hours, at the above 

FOR FURTHER INFORMATION CONTACT: Susan Moore or Ken Sanchez at the 
above address (telephone at 916/414-6600; facsimile at 916/414-6710).



    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition 
to revise the List of Threatened and Endangered Species that presented 
substantial scientific or commercial information that listing may be 
warranted, we make a finding within 12 months of receiving the petition 
on whether the petitioned action is: (a) Not warranted, (b) warranted, 
or (c) warranted but precluded by other pending proposals. Such 12-
month findings are to be published promptly in the Federal Register.
    On April 3, 2000, we received a petition dated April 2000, from the 
Center for Biological Diversity, Tucson, Arizona, and Sierra Nevada 
Forest Protection Campaign, Sacramento, California, and other 
organizations to list as threatened or endangered the California 
spotted owl (Strix occidentalis occidentalis). The names, addresses, 
and signatures of representatives of these organizations followed in a 
letter dated April 17, 2000. These organizations filed the petition on 
behalf of themselves and 14 other organizations and requested that we 
designate critical habitat for the California spotted owl concurrent 
with listing. Further, they requested emergency listing and emergency 
designation of critical habitat. Although emergency listing and 
designation of critical habitat are not petitionable actions under the 
Act, we determined that an emergency situation did not exist.
    On October 12, 2000, we published a 90-day finding on that petition 
in the Federal Register (65 FR 60605). In that publication we found 
that the petition

[[Page 7581]]

presented substantial scientific or commercial information to indicate 
that listing the California spotted owl may be warranted, and we 
requested information and data regarding the species. On July 31, 2001, 
the Center for Biological Diversity and others filed a complaint in 
District Court, alleging the Service failed to make a timely 12-month 
finding in response to their listing petition. On March 5, 2002, the 
District Court entered an order requiring the completion of the 12-
month finding by February 10, 2003.

The Petition

    The petitioners believe that listing the California spotted owl is 
necessary because of factors related to loss and modification of 
habitats from timber harvest and urbanization, lack of existing State 
or Federal regulatory mechanisms that protect the species, and declines 
in the population.
    The petitioners believe listing is necessary primarily because past 
timber harvest in the Sierra Nevada has resulted in the loss of key 
components of spotted owl habitat over large portions of the landscape. 
They also believe that current Federal land management agency 
strategies and private land forest practices are resulting in the loss 
or destruction of spotted owl habitat. They expressed special concern 
about past timber harvest practices that selectively removed the 
larger, older trees that comprise a key component of spotted owl 
breeding habitat.
    The petitioners refer to the ``Interim Guidelines'' of the Federal 
land management strategy in place at the time the petition was 
submitted (April 2000) to conclude that current and planned timber 
sales would continue to remove key components of spotted owl habitat. 
The petitioners believe the cumulative effects of continued timber 
harvest and fuels reduction projects on Federal lands would have 
dramatic effects on the spotted owl.
    The petitioners state, ``* * * there are almost no protections for 
spotted owls * * *'' on private lands. They assessed the State 
mechanism for permitting timber harvest and analyzed recent timber 
harvest plans to conclude, ``* * * owls are being heavily impacted by 
logging on private lands.'' Additional evidence of habitat destruction 
cited by the petitioners includes urbanization and development, 
particularly loss of habitat at lower elevations from new home 
    The petitioners cite recent studies that report potential 
population declines as further evidence to support a positive listing 
decision. The petitioners review and interpret several studies of 
California spotted owl population dynamics to infer ``drastic'' annual 
declines in the population.
    Other impacts addressed in the petition include livestock grazing, 
recreation, climate change, fire, competition from the barred owl, and 
disease and predation. These are impacts thought by the petitioners to 
be apparent, though not well studied or documented.

Taxonomy and Description

    The spotted owl was first described as Syrnium occidentale by John 
Xantus in 1859 based on a specimen collected at Fort Tejon, Kern 
County, California (Xantus 1859). The species was later reassigned to 
the genus Strix (Ridgway 1914). The specific name was altered to 
conform to the Code of Zoological Nomenclature, yielding the scientific 
name Strix occidentalis (Service 1993). Currently, the American 
Ornithologist Union (AOU) recognizes three subspecies of spotted owls: 
the California spotted owl (Strix occidentalis occidentalis), the 
northern spotted owl (Strix occidentalis caurina), and the Mexican 
spotted owl (Strix occidentalis lucida) (AOU 1957).
    The spotted owl is mottled in appearance. It has a brown back with 
white spots and brown barring. The facial disk is pale brown with 
concentric rings of dark brown, bordered by a ring of dark brown 
feathers. A conspicuous light-colored ``X'' is apparent between the 
eyes above its pale yellowish beak, where ``eyebrows'' and ``whiskers'' 
merge together. Unlike most other owl species, which have yellow eyes, 
spotted owls have dark brown eyes. Wings and tail are rounded, and all 
flight feathers are dark brown with light brown cross-bars. Sexes 
cannot be distinguished by plumage, but can be readily identified by 
size and vocalization (Verner et al. 1992b). Females are usually larger 
than males, with males weighing 470 to 685 grams (g) (17 to 24 ounces 
(oz)), and females 535 to 775 g (19 to 27 oz) (Gutierrez et al. 1995). 
First- and second-year adults can be distinguished by the tips of the 
tail feathers, which are white and taper to a sharp point until 
replaced by adult plumage at about 26 months of age (Gutierrez et al. 
1995). The spotted owl is the fifth largest species of owl occurring in 
North America (Verner et al. 1992b); It is 41 to 48 centimeters (cm) 
(16 to 19 inches (in)) in length, with a wingspan of 107 to 114 cm (42 
to 45 in) (Center for Biological Diversity 2000).
    California spotted owls are lighter brown with slightly larger 
white spots than the northern spotted owl. Mexican spotted owls are 
lighter brown than both the California and northern subspecies, with 
some individuals having a rare palomino color. The facial disk and 
upper breast of the Mexican spotted owl contain more white than the 
other subspecies, and larger white spots add to the perception that 
they are lighter in color (Gutierrez et al. 1995).
    The northern spotted owl was listed as threatened under the Act in 
1990 (Service 1990), and the Mexican spotted owl was listed as 
threatened in 1993 (Service 1993).

Population Genetics

    Three genetic markers (i.e., allozymes, mitochondrial DNA and 
random amplified polymorphic DNA) have been used to examine the genetic 
structure of spotted owls . Analysis of allozymes (alternate forms of 
proteins) supports separation of the Mexican spotted owl from the other 
two subspecies (Guti[eacute]rrez et al. 1995). Barrowclough et al. 
(1999) compared the sequences of a fragment of mitochondrial DNA 
(mtDNA) from 73 individual spotted owls, including samples from all 
three subspecies and from multiple populations within each subspecies. 
Their data support the separation of the species into the three 
currently recognized subspecies. Based on their data, the northern 
spotted owl appears to have diverged from the other two subspecies, and 
the California spotted owl later diverged from the Mexican spotted owl. 
In this study, gene flow appeared relatively high within subspecies and 
low between subspecies (Barrowclough et al. 1999). The authors 
concluded that gene flow between northern and California spotted owls 
is a recent and uncommon phenomenon.
    Haig et al. (2001) used random amplified polymorphic DNA (RAPD) to 
analyze genetic variation between spotted owls at multiple geographic 
levels, including between subspecies. They found extremely low RAPD 
variation in spotted owls, with only 11 of 400 primers showing 
variation. Their data show genetic separation of Mexican spotted owls 
from California and northern spotted owls, but do not show separation 
between the California and northern subspecies. They suggest that the 
lack of separation between the California and northern subspecies in 
their data may be due to recent gene flow between subspecies, or due to 
the low variation of the data. We are also aware that additional 
research by Haig and colleagues bearing on the question of subspecific 
distinctions in spotted owls has not yet been published (A. Bowers, 
U.S. Fish and Wildlife Service, in litt. 2002).

[[Page 7582]]

    Currently available, published genetic data (i.e., mtDNA and RAPDs) 
apparently lead to different conclusions regarding subspecific 
distinctions in spotted owls. Therefore, for the purposes of this 
finding, we adopt the taxonomy accepted by the American Ornithological 
Union (AOU 1957), which recognizes the California spotted owl as a 
distinct subspecies (Strix occidentalis occidentalis).

Life History

    Mating System and Reproduction. Spotted owls usually reach 
reproductive maturity at two years of age, although first year birds 
have sometimes nested the season after they were hatched. Considerable 
variation exists in both the percentage of pairs that nest and the 
number of pairs that successfully fledge young, both geographically and 
from year to year (Verner et al. 1992b).
    Spotted owls are monogamous with no records of extra-pair 
copulations. They usually pair with the same mate from year to year, 
although ``divorces'' have been documented. The breeding season of 
California spotted owls extends from mid-February to mid-September or 
early October. Individuals begin breeding earlier in the San Bernardino 
Mountains than in the Sierra Nevada. Within a geographic area, 
individuals begin breeding earlier at lower elevations (Verner et al. 
    California spotted owls are mostly nonmigratory, remaining within 
the same home ranges year round. However, in the Sierra Nevada, some 
individuals migrate downslope to winter habitats (Verner et al.1992b). 
Laymon (1988) observed the subspecies migrating from summer home ranges 
in mixed conifer forests to winter home ranges in lower elevation pine-
oak woodlands. He believed that similar migrations may also occur in 
Southern California. Tibstra (1999) observed that 10 of 22 dispersing 
juvenile owls having natal sites in coniferous forest habitats above 
1,120 meters (m) (3,675 feet (ft)) moved downslope to lower elevation 
(305 m (1,000 ft) to 732 m (2,402 ft)) pine-oak woodland habitats. Of 
those ten, data were available through the following spring for only 
two, both of which overwintered and then moved back to high-elevation 
sites. The elevational movements of those two owls were significantly 
correlated with environmental temperature. Tibstra speculated that the 
pattern of migration to winter range observed in some adults may be 
established in the first year by dispersing juveniles.
    Owls that migrate downslope do so between early October and mid-
December and return in late February to late March. Such migrations 
range from 15 to 65 kilometers (km) (9 to 40 miles (mi)) with 
altitudinal changes of 500 to 1,500 m (1,640 to 4,921 ft). Some 
individuals have also been observed to move between high- and low-
elevation ranges one or more times within a single winter 
(Guti[eacute]rrez et al. 1995).
    Individuals of migratory pairs of California spotted owls migrate 
to separate winter ranges rather than wintering together. After they 
return to their summer ranges, they follow the same breeding cycle as 
nonmigratory pairs, as described below. However, they probably do not 
spend as much time together at the beginning of the breeding season, 
because they may not return from their winter range by the time 
nonmigratory pairs have begun roosting together (Verner et al. 1992b, 
Guti[eacute]rrez et al. 1995). Individuals of nonmigratory pairs of 
California spotted owls remain together on the same home range year 
round, but they do not usually roost together during the winter. 
However, late in the winter, they increasingly roost together, preen 
each other, and occasionally copulate. For approximately two weeks 
before the first egg is laid, pairs roost together and copulate once or 
twice each evening. For about one week before the first egg is laid, 
the female spends most of her time near the nest, and the male brings 
her prey items (Verner et al. 1992b, Guti[eacute]rrez et al. 1995).
    California spotted owl eggs are elliptical, white to pearl grey, 
and smooth to slightly granular in texture. California spotted owl egg 
laying peaks in mid-April. When egg laying begins, the female spends 
almost all her time in the nest, and the male supplies almost all of 
her food. The number of eggs in clutches ranges from one to four, with 
most nests containing two. Successive eggs are laid approximately three 
days apart. Pairs continue to copulate throughout, and for up to four 
days, after the egg laying period (Verner et al. 1992b, 
Guti[eacute]rrez et al. 1995).
    Only the female incubates the eggs. During the first two days of 
incubation, she may leave the nest for up to two hours, but thereafter 
she will only leave the nest for 10 to 20 minutes at a time to 
regurgitate pellets, defecate, preen, or accept food from her mate 
(Verner et al. 1992b).
    Eggs hatch after approximately 30 days. Hatchlings are covered with 
white natal down, with juvenile plumage starting to replace natal down 
at about 10 to 20 days (Guti[eacute]rrez et al. 1995). The female 
broods the hatchlings almost continuously for eight to ten days. During 
this period, the male supplies food for the female and young. Two to 
three weeks after the eggs hatch, the female begins foraging for one to 
four hours per night. Males have not been observed to feed the chicks 
directly, but continue to bring food to the nest, which the female 
passes to the chicks (Verner et al. 1992b).
    Most chicks fledge 34 to 36 days after hatching. New fledglings are 
weak fliers and may spend hours or days on the ground. Approximately 
three days after fledging, most young are able to fly or climb to 
elevated perches. Within a week, most are able to fly between trees. 
Both parents continue to feed the fledglings until mid to late 
September (Verner et al. 1992, Guti[eacute]rrez et al. 1995).
    Dispersal. Spotted owls primarily disperse as juveniles (natal 
dispersal), but may also disperse as adults (breeding dispersal) if 
habitat within their home range has been degraded or if they have 
separated from a mate (Verner et al. 1992b). Natal dispersal occurs in 
September and October.
    Natal dispersal distances of California spotted owls have been 
estimated using radio telemetry (Verner et al. 1992, Tibstra 1999) and 
recapturing territorial owls that were banded as juveniles (LaHaye et 
al. 2001, Jennifer Blakesley, Colorado State University, in litt. 
2002a). Dispersal distances of successfully dispersing owls ranged from 
3 km (2 mi) to 76 km (47 mi). Mean natal dispersal distance of 26 owls 
in the Sierra National Forest and Sequoia National Park estimated using 
radio telemetry was 15.9 km (9.9 mi) (Tibstra 1999) and median distance 
of 42 owls on the Lassen National Forest estimated using recapture data 
was 25 km (16 mi) for females and 23 km (14 mi) for males (Blakesley in 
litt. 2002a). Mean natal dispersal distances of 129 owls in southern 
California estimated using recapture data were 10.1 km (6.3 mi) for 
males and 11.7 km (7.3 mi) for females. No significant difference 
existed in dispersal distance or time to become territorial between 
sexes (LaHaye et al. 2001). In this study, some dispersing owls did not 
occupy territories until they were four years old, but over 60 percent 
occupied territories within one year of fledging. Apparent survival of 
fledglings (calculated as the percentage of banded fledglings that were 
later relocated) was 31.8 percent.
    LaHaye et al. (2001) concluded that the presence of conspecifics 
(members of the same species) may play a vital role in the recruitment 
of dispersing California spotted owls into a territory, because owls 
that ``settled'' (established territories) were significantly more 
likely to do so in territories that were occupied the previous year 
than would

[[Page 7583]]

be expected by chance and all previously vacant territories that were 
settled were adjacent to occupied territories. The percentage of 
territories occupied varied from 59 to 95 percent from year to year. 
During the study, young fledged from 28 percent of the 39 territories 
that were ``frequently vacant,'' indicating that habitat at those sites 
was suitable to support California spotted owl reproduction.
    Four color banded adults on the Sierra National Forest later 
shifted territories, moving 3.4 km (2.1 mi), 3.5 km (2.2 mi), 3.9 km 
(2.4 mi), and 7.1 km (4.4 mi) (Verner et al. 1992b). In a study of 
breeding dispersal of California spotted owls in the San Bernardino 
Mountains (LaHaye and Guti[eacute]rrez in litt. 2002), 46 females and 
38 males dispersed, which were 22 percent and 17 percent of the total 
banded females and males, respectively. Among dispersing females, 70 
percent were adults and 30 percent subadults; among males, 71 percent 
were adults and 29 percent were subadults. A significantly higher 
percentage of subadults dispersed (30 percent) compared to the 
territorial population as a whole (14 percent). Mean dispersal 
distances were 4.3 km (2.7 mi) for females and 3.0 km (1.9 mi) for 
males, which are significantly shorter than natal dispersal distances 
observed in the same population.
    Interactions with Other Species and Natural Mortality. Spotted owls 
are mobbed by many species of diurnal birds (Gutierrez et al. 1995). 
Red-tailed hawks (Buteo jamaicensis) and common ravens (Corvus corax) 
may take away prey items that are captured by spotted owls. The spotted 
owl's closest competitors are great horned owls (Bubo virginianus) and 
barred owls (Strix varia). Barred owls have recently colonized portions 
of the range of California spotted owls and are known to displace 
spotted owls from their territories (Verner et al. 1992b, 
Guti[eacute]rrez et al. 1995). Circumstantial evidence suggests that 
barred owls may kill spotted owls (Leskiw and Guti[eacute]rrez 1998). 
Northern goshawks (Accipiter gentilis), great horned owls, red-tailed 
hawks and potentially other birds of prey eat spotted owls (Verner et 
al. 1992, Guti[eacute]rrez et al. 1995). Fishers (Martes pennanti) have 
been observed in spotted owl nest trees and may take eggs or chicks 
(Guti[eacute]rrez et al. 1995).
    Starvation (Verner et al. 1992b, Guti[eacute]rrez et al. 1995, 
Tibstra 1999) has been documented as a cause of death in California 
spotted owls. Starvation is more common in juveniles than adults and 
may result from low prey availability or lack of hunting experience 
(Verner et al. 1992b). Dispersing juveniles sometimes roost in open 
habitats during inclement weather, which may result in exposure causing 
or contributing to their deaths (Guti[eacute]rrez et al. 1995). 
Accidents leading to death have been documented for spotted owls, 
including flying into obstacles and drowning (Verner et al. 1992b).
    Feeding and Metabolism. Spotted owls are ``perch and pounce'' 
predators, hunting primarily by selecting an elevated perch, detecting 
prey by sight or sound, and swooping from the perch to capture the prey 
with their talons. Spotted owls are not fast fliers, but they are very 
agile and maneuverable. The flight pattern is a series of quick wing 
beats interspersed with gliding flight. Spotted owls use gliding flight 
when approaching prey. When gaining altitude in the forest canopy, they 
make a series of short climbing flights rather than one continuous 
flight. Flight is labored when attempting to fly to a higher perch or a 
nest sight. Flight above the forest canopy is probably rare, except 
during dispersal (Guti[eacute]rrez et al. 1995). If a potential prey 
item is inaccessible or at a considerable distance from an owl's perch, 
the owl may move closer before pouncing (Verner et al. 1992b). Spotted 
owls will forage at several sites within a single night 
(Guti[eacute]rrez et al. 1995). They also hunt by capturing in mid-air 
flying prey such as insects, bats, and birds (Verner et al. 1992b, 
Guti[eacute]rrez et al. 1995). California spotted owls forage primarily 
at night, but have been observed hunting during the day, especially 
while raising young (Laymon 1991, Verner et al. 1992). They may cache 
prey items on limbs, stumps, or the ground for later consumption 
(Guti[eacute]rrez et al. 1995). Prey items include mammals, birds, and 
    Spotted owls have a high water need relative to their metabolic 
rate (Weathers et al. 2001), and have been observed drinking surface 
water from seeps and creeks (Guti[eacute]rrez et al.1995). California 
spotted owls have a narrow thermal neutral zone (the ambient 
temperature range through which a bird or mammal can maintain its 
normal body temperature without expending energy to do so) relative to 
birds in general and are therefore especially subject to heat stress 
(Guti[eacute]rrez et al. 1995, Weathers et al. 2001). They roost higher 
in the forest canopy during winter and lower during the summer. They 
will also move during a day in response to changes in ambient 
temperature and sun exposure. The variety of microclimates available in 
mature and old growth forests has been postulated as an explanation for 
the spotted owl's use of such habitats (Guti[eacute]rrez et al. 1995).

Distribution, Range, and Land Ownership

    Grinnell and Miller (1944) described the range of the California 
spotted owl as ``[I]n general, coastal slope of southern California 
from southern San Diego County northwest to Santa Barbara, Ventura, and 
western Kern Counties, and west flank of Sierra Nevada north from 
Tulare County to Tehama County'' and noted that the southern California 
range was apparently separated from the Sierra portion of the range.
    The mapped range of the California subspecies in Grinnell and 
Miller (1944) indicated a gap in the distribution of spotted owls in 
Shasta County, separating the California and northern spotted owl 
subspecies. However, based on newer records and the occurrence of 
apparently-suitable habitat in the area, more recent authors have 
concluded that this purported gap between the California and northern 
subspecies may not have actually existed (Detrich et al. 1993). For 
regulatory purposes, we established the ``Pit River area'' as the 
boundary between the northern spotted owl and the California spotted 
owl (55 FR 26114). No historic data are available regarding pre-
European settlement population numbers of the California spotted owl.
    The northern spotted owl ranges from southwestern British Columbia, 
Canada through western Washington, western Oregon, and northern 
California south along the coast to San Francisco Bay (Service 1990). 
The range of the Mexican spotted owl is disjunct from the other 
subspecies, from southern Utah and Colorado south through Arizona and 
New Mexico, and is discontinuous through the Sierra Madre Occidental 
and Oriental to the mountains at the southern end of the Mexican 
Plateau (Service 1993).
    Today the California spotted owl still occurs throughout its 
historic range, including the west side of the Sierra Nevada from 
Shasta County south to the Tehachapi Pass, and all major mountains of 
southern California, including the San Bernardino, San Gabriel, 
Tehachapi, north and south Santa Lucia, Santa Ana, Liebre/Sawmill, San 
Diego, San Jacinto, and Los Padres ranges (Beck and Gould 1992). In 
addition, a few sites have been found on the eastern side of the Sierra 
Nevada and in the central Coast Ranges at least as far north as 
Monterey County.
    Regarding the current distribution of the California spotted owl, 
Verner et al. (1992a) stated ``in spite of the fact that

[[Page 7584]]

logging has occurred over nearly all of the conifer forests of the 
Sierra Nevada in the past 100 years, and especially the past 50 years, 
spotted owls continue to be widely distributed throughout most of the 
conifer zone. Indeed, spotted owls may be more abundant in some areas 
of the Sierra Nevada today than they were 100 years ago, `` (due to 
presumed effects of 19th century sheep grazing on spotted owl prey 
species.) They also stated that ``Spotted owl distribution in the 
Sierra Nevada is characterized by its continuity and relatively uniform 
    The elevation of known nest sites of California spotted owls ranges 
from about 305 to 2,348 m (1,000 to 7,700 ft), with approximately 86 
percent of sites occurring between 915 and 2,135 m (3,000 and 7,000 ft) 
(USFS 2001a). In conifer forests mean elevation of nest sites was 1,160 
m (5,300 ft) in the northern Sierra Nevada and 1,830 m (6,000 ft) in 
southern California (Guti[eacute]rrez et al.1992).
    The California Department of Fish and Game (CDFG) has maintained a 
database of the number and location of California spotted owl 
territories located from the early 1970s to the present. We have 
combined that database with similar data collected by Sierra Pacific 
Industries, the major private timberland owner in the Sierra Nevada. 
The following discussion of locations and land ownership is based on 
that combined database and includes all records available to us. It is 
important to note that not all territories are occupied during any 
given year. The data presented are useful to illustrate the range of 
the species and jurisdictions under which it occurs, but should not be 
viewed as a population estimate because the current status of many 
territories is unknown due to lack of recent surveys; not all 
territories are occupied in a given year; and, in addition to 
territorial owls that comprise most of the sites in the database, 
nonterritorial, ``floater'' owls may be present but uncounted.
    California spotted owl territories have been located on Forest 
Service (USFS), National Park Service (NPS), Bureau of Land Management 
(BLM), California Department of Parks and Recreation (State parks), 
California Department of Forestry and Fire Protection (CDF), California 
State Lands Commission (CSLC), Native American and private lands, and 
in Mexico.
    Sierra Nevada. In the Sierra Nevada the California spotted owl is 
mostly continuously and uniformly distributed, with several breaks in 
distribution where habitat appears limited due to natural or human-
caused factors (Beck and Gould 1992). These Areas of Concern are 
further discussed in a later section.
    In Sierra Nevada national forests, 99 percent of owl sites occur on 
the Lassen, Plumas, Tahoe, Eldorado, Stanislaus, Sierra, and Sequoia 
National Forests. The number of territories per national forest are as 
follows: Modoc 3, Lassen 138, Toiyabe 2, Inyo 5, Tahoe 173, Lake Tahoe 
Basin Management Unit 14, Plumas 254, El Dorado 202, Stanislaus 234, 
Sierra 226, and Sequoia 148. This results in a sub-total for Forest 
Service Sierran lands of 1,399 sites. The number of territories per 
national park are as follows: Lassen 6, Kings Canyon 19, Sequoia 50, 
and Yosemite 54. Fourteen territories are on BLM land in the Sierra 
Nevada. Three territories are on State parks, 1 is on CDF land, and 4 
are on CSLC land. One territory is on Native American land and 314 are 
on private lands. Thus, the total number of California spotted owl 
sites known in the Sierra Nevada is 1,865 (Service 2002)
    Because the subspecies has large home ranges, a given home range 
may occur across different ownerships. For instance, the Forest Service 
reported that over 15 percent of 135 Forest Service sites analyzed had 
greater than 15 percent of their theoretical home range on private 
lands (USFS 2001).
    Coast Ranges and Southern California. In southern California, the 
owl occupies ``islands'' of high elevation forests isolated by lowlands 
covered by chaparral, desert scrub, and increasingly (Noon and McKelvey 
1992), human development (LaHaye et al.1994). California spotted owls 
have been found on 440 territories or sites in southern California in 
15 populations comprised of 3 to 270 individuals, and separated from 
each other by 10 to 72 km (6 to 45 mi) (Verner et al. 1992a, 
Guti[eacute]rrez 1994). Seventy-five percent of known territories are 
on Federal lands and twenty-five percent are on nonFederal lands. The 
Angeles National Forest has 64 territories, Cleveland National Forest 
has 18 territories, Los Padres National Forest has 109 territories, and 
San Bernardino National Forest has 138 territories; two territories are 
on BLM land; eight territories are on State parks; six are on Native 
American lands, 95 are on private lands, and one is in Mexico.
    Within the California coastal and inland mountain ranges where 
California spotted owls occur (San Bernardo, San Gabriel, San Jacinto, 
Castaic, Santa Ana, and Santa Lucia mountains and San Diego/Peninsular, 
and Los Padres Ranges ) an area of just over 2,428,068 hectares (ha) 
(6,000,000 acres (ac)) was assessed for all habitats by the Forest 
Service (Stephenson and Calcarone 1999). Landownership in the 
assessment area is National Forest (57 percent), private (33 percent), 
BLM (4 percent), Indian (3 percent), State (2 percent), military (1 
percent) and local (1 percent). Not all of the analysis area is 
suitable spotted owl habitat (mixed conifer hardwood), thus the portion 
of the total owl population or sites known on Federal lands as 
determined in Verner et al.1992a and Guti[eacute]rrez 1994, is higher 
(75 percent) than their relative ownership in the assessment area (62 
    The range of California spotted owls in southern California is 
disjunct from that in the Sierra Nevada range as a result of natural 
topographic and manmade factors (Stephenson and Calcarone 1999). Within 
this southern range, habitat and spotted owls are distributed 
discontinuously across the landscape reflecting natural vegetation 
breaks, topographic conditions, and human induced habitat disturbance 
and fragmentation (Noon and McKelvey 1992). The spotted owls in the 
southern portion of the range may function as a meta population, with 
separate subpopulations connected by infrequent but persistent 
interchange of individual owls (Noon and McKelvey 1992; LaHaye et al. 


    The habitat used by California spotted owls today is comprised of 
forests that have been shaped by numerous inter-acting human impacts, 
including timber harvest, livestock grazing, urbanization, and, because 
of fire suppression, changes in the character of wildfires. Prior to 
the occupation of California by Anglo-Americans in the mid-1900s, 
habitat was probably fairly stable on a large geographic scale, 
although there were almost certainly localized variations caused by 
fire and other causes of forest mortality. In recent decades, timber 
harvest and ingrowth related to fire suppression have created 
widespread forest conditions believed to be considerably different than 
that of pre-historic times (McKelvey and Weatherspoon 1992, McKelvey 
and Johnston 1992). In the following section, the current understanding 
of use of today's forests by California spotted owls will be portrayed, 
along with some discussion of the factors that created these 
conditions. The anticipated trends in habitat will be discussed in the 
Threats section below.
    The suppression of wildfire during the 20th century has been one of 
the most important factors in creating the forest conditions that 
provide habitat for

[[Page 7585]]

the California spotted owl today. For thousands of years preceding 
European settlement of California, low to moderate intensity fires 
burned frequently in most Sierra Nevada vegetation types (University of 
California 1996). Median fire return intervals were typically less than 
20 years, and as low as four years, in ponderosa pine (Pinus ponderosa) 
and mixed conifer zones. In the mixed conifer zone, where approximately 
80 percent of Sierra Nevada California spotted owl sites occur (see 
Habitat Requirements, above), many plant species take advantage of, or 
depend on, fire for their reproduction or as a means of competing with 
other species. The effects of frequent surface fires largely explain 
the reports and photographs by early observers who described Sierra 
Nevada forests as typically open and park-like. However, other early 
observers reported dense conditions and dark or impenetrable forest. 
These records suggest that although open conditions were more prominent 
than they are today, Sierra Nevada forests were a mix of different 
degrees of openness, with an unknown proportion in dark, dense, nearly 
impenetrable vegetative cover and with variations in density with 
latitude, aspect, and elevation (University of California 1996, Gruell 
    Suppression of wildland fires had been established in California as 
State and Federal policy by the early 20th century. The area burned 
annually in recent times has been estimated to be only about three 
percent of that burned pre-European settlement in mixed conifer forest 
types (University of California 1996). As will be discussed further 
below, fire suppression has resulted in substantial growth of small 
understory trees in much of the range of the California spotted owl.
    Timber harvest has been another obvious impact to California 
spotted owl habitat (Guti[eacute]rrez 1994, Verner et al. 1992a). 
McKelvey and Johnston (1992) used historical documents to describe the 
status of Sierran forests at the beginning of the 20th century, and 
detailed the harvest history from the late 19th century to 1990. 
Harvest steadily intensified from the railroad building and mining eras 
of the 1800s until the 1950s, then remained at relatively high levels 
through the 1980s. (Intermittent declines occurred during poor economic 
conditions of the 1930s and early 1980s.) Low elevations and accessible 
areas (McKelvey and Johnston 1992, Beardsley et al. 1999) and 
commercially important forest types such as west-side mixed conifer and 
east-side pine (Franklin and Fites-Kaufmann 1996) have been the most 
heavily impacted. As a result, McKelvey and Johnston stated that ``The 
mixed conifer zone of the Sierra Nevada * * * has few or no stands 
remaining that can be described as natural or pristine.''
    Verner et al. (1992a) discussed five major factors of concern for 
California spotted owl habitat that have resulted from historical 
timber harvest strategies: (1) Decline in the abundance of very large, 
old trees; (2) decline in snag density; (3) decline in large-diameter 
logs; (4) disturbance or removal of duff and topsoil layers; and (5) 
change in the composition of tree species. Of these concerns, they 
believed significant changes in diameter distributions of trees in the 
Sierra Nevada and rapid reductions in the distribution and abundance of 
large, old, and decadent trees posed the greatest threat to the 
California spotted owl. Thus, extensive commercial harvest of large old 
trees in late successional forest directly affected the key structural 
components of California spotted owl habitat.
    Timber harvest in the Sierra Nevada peaked in the 1950s and 
remained at high levels into the late 1980s (McKelvey and Johnston 
1992). Since the late 1980s, the volume of timber harvested in the 
Sierra Nevada has declined substantially. In particular, levels of 
timber harvest on national forest lands declined after implementation 
of the California Spotted Owl Sierran Province Interim Guidelines in 
1993 (USFS 2001a). From Fiscal Year (FY)1998 through FY 2002, the mean 
annual total harvest volume (279.4 million board ft (mmbf)) on the 
seven National Forests that support most of the Sierra owl population 
was about 28 percent of the mean annual total volume harvested on those 
forests during the period FY 1986 through FY 1990 (1,007 mmbf) (USFS 
2002a). Whereas old-growth accounted for most of the volume in the 
past, more recent harvest practices have focused on thinning of young, 
smaller trees (McKelvey and Johnston 1992).
    The decline in Federal harvest led an overall decline in the total 
Federal and private harvest in the Sierra Nevada. According to 
California timber tax data (California Board of Equalization 2002), 
total harvest from public lands in 18 Sierra Nevada counties during the 
late 1980s and early 1990s constituted about half of the total annual 
volume harvested in those counties, but following the 1993 
implementation of protections for the California spotted owl on Forest 
Service lands, the public lands harvest did not exceed 25 percent of 
the total annual volume harvested from those counties in any year from 
1994 through 2000. In the meantime, private harvest during the 15-year 
period from 1986 to 2000 remained between 650 and 775 mmbf per year, 
except for a 2-year spike of over 900 mmbf per year in 1990 and 1991. 
Mean annual volume from private lands in the 18 Sierra Nevada Counties 
in the period for the period 1986 to 1990 was about 811 mmbf, and mean 
annual volume from 1996 to 2000 was about 714 mmbf, a difference of 12 
percent. Thus, in the Sierra Nevada, private lands harvest has declined 
somewhat while Federal harvest has declined sharply since the late 
    Similar trends in timber harvest have occurred in the four southern 
California national forests, although timber harvest in this area was 
never as extensive as in the Sierra Nevada. According to McKelvey and 
Johnston (1992), harvest volume in Los Angeles and San Bernardino 
counties was about ten to twenty times higher in the 1960s than in the 
early 1980s, and the decline has continued since the 1980s. Southern 
California national forests have not had a commercial green timber sale 
program for over a decade. Harvest in recent years has primarily been 
salvage and hazard trees along roads and near administrative sites (M. 
Gertsch, USFS, pers. comm. 2002). Mean annual total harvest volume for 
the four forests in FY 1998 to 2002 (1.66 mmbf) was about 30 percent of 
the mean annual total harvested on the four forests during FY 1988 
to1992 (5.48 mmbf) (USFS 2002a).
    Thus, timber harvest, the primary cause of habitat loss for the 
California spotted owls for decades, has been much reduced in recent 
years. Spotted owls today are occupying habitat that is a combination 
of the remnants of older stands and stands regenerating from timber 
harvest in past decades. The present habitat used by California spotted 
owls is further described below.
    California spotted owls use a broader range of habitat types than 
the northern spotted owl (Call et al. 1992, Guti[eacute]rrez et al. 
1992, Anderson and Mahato 1995, Moen and Guti[eacute]rrez 1997, North 
et al. 2000), in part due to the relatively more complex landscapes 
available to the California subspecies (Zabel et al. 1992b, Franklin 
and Fites-Kaufmann 1996, Helms and Tappeiner 1996, Beardsley et al. 
1999). In the Sierra Nevada, this complexity reflects: (1) The variety 
of environmental conditions due to elevation, latitude, geology, 
precipitation, and temperature; (2) rich flora; and (3) influence of 
natural disturbance, especially fire (Andersen and Mahato 1995) and 
human disturbance (Franklin and Fites-Kaufmann 1996). The forests of 

[[Page 7586]]

Sierra Nevada have a complex logging history dominated by selection 
methods (McKelvey and Johnston 1992, Beardsley et al.1999) varying by 
number of entries, types of species harvested, size distribution of 
harvested trees, and total volume logged (Zabel et al.1992b). The 
heterogeneity of forests occupied by California spotted owls make 
quantifying its habitat difficult and sensitive to scale. Several 
studies have found that analysis of habitat at a coarse, small scale 
(e.g., using timber type polygons developed for timber management) 
masks fine grained attributes used or selected by owls (Bias and 
Guti[eacute]rrez 1992, Zabel et al.1992a, Moen and Guti[eacute]rrez 
    Despite the complexity of California spotted owl habitat, several 
authors have concluded the subspecies is a habitat specialist (Andersen 
and Mahato 1995, Moen and Guti[eacute]rrez 1997, LaHaye et al.1997), 
selecting habitat at several scales. California spotted owls, like the 
other subspecies of spotted owls, use or select habitats for nesting, 
roosting, or foraging that have structural components of old forests, 
including large (typically greater than 61 cm (24 in) diameter at 
breast height (dbh; breast height has been standardized at 137 cm (4.5 
ft) above the ground) (Call 1990, Guti[eacute]rrez et al.1992, Zabel et 
al.1992a, Moen and Guti[eacute]rrez 1997, USFS 2001a), decadent trees 
(trees with cavities, broken tops, etc.); high density of trees (Laymon 
1988, Call 1990, Bias and Guti[eacute]rrez 1992, Guti[eacute]rrez et 
al.1992, LaHaye et al.1997, Moen and Gutirrez 1997); multi-layered 
canopy/complex structure (Call 1990, Guti[eacute]rrez et al.1992, 
LaHaye et al.1997, Moen and Guti[eacute]rrez 1997); high canopy cover 
(greater than 40 percent and mostly greater than 70 percent; Laymon 
1988, Bias and Guti[eacute]rrez 1992, LaHaye et al.1992, 
Guti[eacute]rrez et al.1992, Zabel et al.1992a, Moen and 
Guti[eacute]rrez 1997, North et al.2000); snags (Laymon 1988, Call 
1990, Bias and Guti[eacute]rrez 1992, Guti[eacute]rrez et al.1992, 
LaHaye et al.1997 ); and logs (Call 1990). Guti[eacute]rrez et al. 
(1992) noted that these characteristics applied to mixed conifer 
forests, because riparian/hardwood forests occupied by California 
spotted owls did not necessarily have these characteristics.
    Late successional forests provide habitat attributes selected by 
California spotted owls, including large trees, high canopy closure, 
multi-layered canopies, snags, and logs (University of California 
1996). The current extent of old forests in the Sierra Nevada is 
believed to be substantially less than in pre-historic times. Estimates 
of the current extent have been made by several authors. The University 
of California (1996) reported that in national parks in the Sierra 
Nevada, which contain the best representation of pre-European 
settlement conditions because only minor areas have been subject to 
timber harvest, 55 percent of forests are in late successional 
conditions, but on all Federal lands in the Sierra Nevada, late 
successional conditions are now found on only 19 percent of forest 
lands. The Forest Service (USFS 2001a) reported that old forest 
conditions have declined from 50 to 90 percent in various vegetation 
types compared to the range of historical conditions. Beardsley et al. 
(1999) estimated that approximately 15 percent of coniferous forests in 
the Sierra Nevada remain in high quality old growth/late successional 
stages; most of these stands are in high elevations and national parks 
(Franklin and Fites-Kaufmann 1996). Most of the remaining high quality 
late successional/old growth habitat in the Sierra Nevada is in public 
ownership; less than two percent of 1,214,000 ha (3 million ac) of 
private land was classified as high quality late successional/old 
growth habitat (Franklin and Fites-Kaufmann 1996).
    California spotted owls in the Sierra Nevada may have undergone at 
least three periods of decline: (1) Elimination of prey species by 
intensive livestock grazing and burning in the 1800s; (2) logging 
beginning in the late 1800s, which removed basic structural elements of 
owl habitat; and (3) recent
California spotted owls in the Sierra Nevada may have undergone at 
least three periods of decline: (1) Elimination of prey species by 
intensive livestock grazing and burning in the 1800s; (2) logging 
beginning in the late 1800s, which removed basic structural elements of 
owl habitat; and (3) recent logging of stands that regenerated 
following initial entry (Guti[eacute]rrez 1994).
    In the early 1990s, researchers expressed concern regarding 
potential lag effects in population decline, in which the negative 
effects of habitat modification might not be observed until subsequent 
years (Noon et al. 1992, Guti[eacute]rrez 1994, LaHaye et al. 1994). 
However, it seems reasonable to presume that the causal mechanisms of 
negative effects ascribed to the high levels of timber harvest circa 
1990 were substantially reduced as timber harvest levels dropped and 
increased protection measures were instituted in the mid- and late-
1990s. In the opinion of the Forest Service (USFS 2001a), it is 
unlikely that recent timber harvest on national forests has caused 
declines in spotted owl populations, although the possibility exists 
that declines are due in part to latent effects of past timber harvest. 
However, because the regeneration of habitat may take several decades, 
modification of habitat components that resulted from past timber 
harvest is probably still affecting the subspecies to various degrees.
    Although late-successional forests with large old trees are 
believed to provide the best habitat for California spotted owls, 
descriptions of suitable habitat derived from habitat use studies often 
also include smaller size classes, and thus, include a greater 
proportion of the landscape than that included in the above estimates 
of older forest extent. In the early 1990s, Verner et al. (1992a) 
estimated the amount of suitable California spotted owl habitat on 
public land. They defined suitable habitat as having canopy cover 
exceeding 40 percent and dominant trees 30 to 36 cm (12 to 14 in) dbh 
or larger, or areas with the potential to reach those values relatively 
rapidly. Their estimates of California spotted owl habitat in the 
Sierra Nevada by jurisdiction were as follows: 1,416,400 ha (3,500,000 
ac) on national forests;186,560 ha (461,000 ac) on national parks; 
27,721 ha (68,500 ac) on BLM lands; and 10,522 ha (26,000 ac) on State 
lands. Their estimates for the Coast ranges and southern California 
were: 218,530 ha (540,000 ac) on national forests; 3,076 ha (7,600 ac) 
on BLM; and 10,117 ha (25,000 ac) held by State and local governments. 
Thus, the total estimated habitat was 1,872,926 ha (4,628,100 ac). An 
undetermined amount of suitable habitat also existed on private and 
Native American lands (Verner et al. 1992a).
    Habitat in the Sierra Nevada. The Final Environmental Impact 
Statement (FEIS) for the Sierra Nevada Framework Amendment (SNFPA) 
(USFS 2001a) estimated the amount of suitable habitat for California 
spotted owls on national forest lands in the Sierra Nevada to be 1.7 
million ha (4.3 million ac). This estimate was about 14 percent higher 
than that of Verner et al. (1992a). The new estimate was based on more 
refined analysis, rather than an actual increase in habitat. This 
constitutes about 59 percent of the forested lands on the Sierra Nevada 
national forests.
    Amounts of habitat on private lands have not been quantified. 
Generally, industrial landowners regard information relevant to timber 
inventories as proprietary. Based on Forest Service data, there were 
about 485,600 ha (1.2 million ac) of industrial timberland in the 
Sierra Nevada as of 1994 (derived from Waddell and Bassett 1997a, 
Waddell and Bassett 1997b, Waddell and Bassett 1997c). National forests 
in the Sierra Nevada include

[[Page 7587]]

approximately 560,000 ha (1.4 million ac) of private land within their 
administrative boundaries. Private land inholdings are much greater in 
extent in the northern national forests (especially the Lassen, Plumas, 
and Tahoe) than in the southern Sierra Nevada forests. Much of the 
private land within the boundary of the Lassen and Plumas National 
Forests is in contiguous blocks, leaving national forest lands also 
fairly contiguous. Most private land on the Tahoe National Forest is in 
checkerboard ownership, and the Eldorado National Forest has a 
combination of checkerboard ownership and large contiguous blocks of 
inholdings. We acknowledge that considerable amounts of suitable 
habitat exist on private lands, especially in the smaller size classes. 
This is reflected in the occurrence of over 300 spotted owl activity 
centers (about 17 percent of the Sierra Nevada total) on private lands.
    The mixed-conifer forest type (sugar pine (Pinus lambertiana), 
ponderosa pine, white fir (Abies concolor), Douglas-fir (Pinus 
lambertiana), giant sequoia (Sequoiadendron giganteum), incense-cedar 
(Calocedrus decurrens), black oak (Q. kelloggii), and red fir (Abies 
magnifica) is the predominant type used by spotted owls in the Sierra 
Nevada: about 80 percent of known sites are found in mixed-conifer 
forest, 10 percent in red fir forest (red and white fir, lodgepole pine 
(Pinus contorta), and quaking aspen (Populus tremuloides), seven 
percent in ponderosa pine/hardwood forest type (ponderosa pine, 
interior live oak (Quercus wislizenii), canyon live oak (Quercus 
chrysolepis), black oak, incense-cedar, white fir, tanoak (Lithocaarpus 
densiflorus), and Pacific madrone (Arbutus menziesii)), and the 
remaining three percent in foothill riparian/hardwood forest 
(cottonwood (Populus ssp.), California sycamore (Platanus racemosa), 
interior live oak, Oregon ash (Fraxinus latifolia), and California 
buckeye (Aesculus californica) and east-side pine (ponderosa and 
Jeffrey pine (P. jeffreyi)) (Verner et al. 1992a, USFS) 2001).
    Six major studies (Gutierrez et al. 1992) have described habitat 
relations of the owl in four areas spanning the length of the Sierra 
Nevada. These studies examined spotted owl habitat use at three scales: 
landscape; home range; and nest, roost, or foraging stand. Based on 
comparisons of time spent by owls in various habitat types to amounts 
of habitat available, owls preferentially use areas with at least 70 
percent canopy cover, use habitats with 40 to 69 percent canopy cover 
in proportion to their availability, and spend less time in areas with 
less than 40 percent canopy cover than might be expected if habitat 
were selected randomly.
    California spotted owls in the Sierra Nevada prefer stands with 
significantly greater canopy cover, total live tree basal area, basal 
area of hardwoods and conifers, and snag basal area for nesting and 
roosting. Owls use stands dominated by trees with dbhs between 30 and 
61 cm (12 and 24 in) and canopy covers between 40 and 100 percent for 
nesting significantly more than expected, based on the proportion of 
those forest types (Gutierrez et al. 1992). Stands suitable for nesting 
and roosting have: (1) Two or more canopy layers; (2) dominant and 
codominant trees in the canopy averaging at least 61 cm (24 in) in dbh; 
(3) at least 70 percent total canopy cover (including the hardwood 
component); (4) higher than average levels of very large, old trees; 
and (5) higher than average levels of snags and downed woody material 
(Gutierrez et al. 1992, USFS 2001a).
    Analysis of vegetation characteristics of plots surrounding 292 
California spotted owl nest and roost sites on the Lassen, Eldorado, 
and Sierra National Forests, and in Sequoia and Kings Canyon National 
Parks provides further information on habitat types favored by the 
species (USFS 2001a). Thirty-two percent of the plots were in stands 
with multilayered canopies exceeding 60 percent closure and with 
average trees exceeding 61 cm (24 in) in dbh. Eighteen percent were in 
stands with 40 to 59 percent canopy closure and with average trees 
exceeding 61 cm (24 in) in dbh. Fourteen percent were in stands with 
over 60 percent canopy cover and with average trees between 28 and 61 
cm (11 to 24 in) in dbh. Eleven percent were in stands with 40 to 59 
percent canopy closure and average trees between 28 and 61 cm (11 to 24 
in) in dbh. Nine percent were in stands with over 60 percent canopy 
closure and average trees exceeding 61 cm (24 in) in dbh. Seven percent 
were in stands with 25 to 39 percent canopy cover and average trees 
exceeding 61 cm (24 in) in dbh. Five percent were in stands with 25 to 
39 percent canopy cover and average trees between 28 and 61 cm (11 to 
24 in) in dbh. North et al. (2000) suggested that canopy cover, tree 
density, and foliage volume represent conditions consistent across 
different forest types and therefore could indicate the basic nest site 
conditions selected by California spotted owls. California spotted owl 
nests were consistently located in sites with 75 percent canopy cover, 
300 trees/ha (122 trees/ac), and 40,000 cubic m/ha (571,860 cubic ft/
ac) of foliage volume.
    Moen and Gutierrez (1997) analyzed California spotted owl habitat 
at the landscape, habitat patch, and microsite levels on a 355 square 
kilometer (137 square mile) study area on the El Dorado National 
Forest. They used remote sensing to analyze vegetation in 457 ha (1,129 
ac) circular plots surrounding spotted owl activity centers, and 
compared those plots with randomly selected plots of equal size. Owl 
plots were significantly more homogeneous than random sites, indicating 
that owls select against patchy or fragmented habitats; owl sites 
contained significantly more area with canopy closure exceeding 70 
percent than random plots; and California spotted owl roosts were 
significantly more likely to be located in mixed conifer habitat 
containing trees greater than 30 cm (12 in) dbh than would be expected 
by chance. In addition, of 82 roost sites examined, 56 (68 percent) 
were in habitat with greater than 40 percent canopy closure and trees 
greater than 30 cm (12 in) dbh, and 97 percent of roost sites had trees 
over 100 cm (39 in) dbh. Microsite comparison between sixteen 0.04 ha 
(0.10 ac) vegetation plots surrounding nest sites and random plots of 
equal area showed that nest plots had significantly higher structural 
diversity, more total trees, larger trees, and more trees over 100 cm 
(39 in) dbh.
    Bias and Guti[eacute]rrez (1992) attributed low use of private 
timberlands by roosting and nesting California spotted owls to 
sanitation (removal of damaged or diseased trees or species of low 
commercial value) and high-grade logging (harvest of large trees of 
high commercial value) that removed potential nest trees. However, as 
stated above, California spotted owls do occur on private timberlands. 
Habitat use by California spotted owls has been studied on a private 
timber production area in the Sierra Nevada, 48 kilometers (km) (30 mi) 
east of Chico, California (Larry L. Irwin et al., National Council for 
Air and Stream Improvement, Incorporated, in litt. 2002). Seven pairs 
of California spotted owls were repeatedly located using 
radiotelemetry. Habitat use was similar to that observed in other 
studies on Federal lands. Owls were located in areas with canopy 
closure averaging 70 percent, dominated by trees 30 to 36 cm (12 to 14 
in) in dbh but with a few larger (over 66 cm (26 in) dbh) trees, and 
with tree densities ranging from 930 to 1,360 trees/ha (372 to 544 
trees/ac). To our knowledge, there are no studies providing information 
on demographic performance of owl populations on private lands in the 
range of the California spotted owl.

[[Page 7588]]

    Habitat in the Coast Range and Southern California. In the coast 
range, California spotted owls occupy redwood/California-laurel forests 
which consists of a mix of coast redwood (Sequoia sempervirens), 
California-laurel (Umbellularia californica), tanoak, Pacific madrone, 
red alder (Alnus rubra), and white alder (Alnus rhombifolia), coast 
live oak, Santa Lucia fir (Abies bracteata), and bigleaf maple (Acer 
macrophyllum) (Verner et al. 1992a). Spotted owls can be found at 
elevations below 305 m (1,000 ft) along the Monterey coast to 
approximately 8,500 ft (2,591 m) in the inland mountains (Stephenson 
and Calcarone 1999). Lower elevation (less than 3,000 ft (914 m)) birds 
can be found in pure oak stands and higher elevation (greater than 
6,500 ft (1,981 m)) birds can be found in pure conifer stands.
    Verner et al. (1992a) noted that California spotted owls also use 
riparian hardwood forest types (coast and canyon live oak, cottonwood, 
California sycamore, white alder, and California laurel) in southern 
California. Owls on Mount San Jacinto used conifer and riparian 
hardwood forests significantly more than would be expected based on 
their availability and owls on Palomar Mountain primarily used conifer 
or mixed forests of conifers and hardwoods. California spotted owl nest 
sites in the San Bernardino Mountains were more likely to be located in 
areas with steeper slopes and in the lower third of canyons and owl 
nest and roost sites in this area were more likely to be located in 
areas with higher canopy closure and higher basal area (the area of all 
trees at breast height) than random sites.
    Spatial positions and vegetation types were compared between plots 
surrounding 144 California spotted owl territory centers and 144 random 
plots in the San Bernardino Mountains of southern California (Smith et 
al. 1999, Humboldt State University, in litt. 2002). Owl sites were 
significantly closer to one another than random sites, showing a 
clumped distribution. Owl sites contained more area of closed canopy 
forest, larger mean patch sizes of closed canopy forest, and lower 
habitat diversity than random sites. California spotted owl territories 
in this study were found in three vegetation types; canyon live oak/ 
big cone Douglas-fir (39 percent of territories), mixed conifer/
hardwood (which includes canyon live oak, big cone Douglas-fir, sugar 
pine, white fir, Coulter pine (P. coulteri), incense cedar, and black 
oak) (28 percent of territories), and mixed conifer (which contains 
white fir, Jeffrey pine, and incense cedar (33 percent of territories).
    Stephenson and Calcarone (1999) estimated that there were 
approximately 473,473 ha (1,170,000 ac) of habitat types where spotted 
owls were known to reproduce (low-elevation oak/bigcone Douglas-fir, 
mid-elevation conifer/hardwood, and high elevation mixed conifer) 
within the range of the subspecies in southern California and the 
central Coast Ranges. The total amount of available suitable habitat in 
the analysis area is likely lower, because it is possible that not all 
habitat is currently in a condition suitable for reproduction, roosting 
or foraging.
    Nest Tree Characteristics. California spotted owls nest in a 
variety of tree/snag species in pre-existing structures such as 
cavities, broken top trees, and platforms such as mistletoe brooms, 
debris platforms and old raptor or squirrel nests (Gutierrez et al. 
1992, 1995). Nest trees are often large, over 89 cm (35 in) average dbh 
(Gutierrez et al. 1992, Steger et al. 1997, LaHaye et al. 1997), and 
larger than other trees in the same stand (Gutierrez et al. 1992). Nest 
trees are also often greater than 200 years old (Gutierrez et al. 1992, 
North et al. 2000). However, approximately 25 percent of nest trees out 
of a sample of over 250 were less than 76 cm (30 in) dbh (Gutierrez et 
al. 1992). Although old, large trees are important to California 
spotted owls, intermediate-sized (28 to 61 cm (11 to 24 in)) trees were 
also selected by nesting (LaHaye et al. 1997; and trees 51 to 76 cm (20 
to 30 in) dbh), roosting (Moen and Gutierrez 1997), and foraging 
(Laymon 1988) owls.
    Prey and Foraging Habitat. California spotted owls are considered 
prey specialists (Verner et al. 1992b) because they select a few key 
species (Verner et al. 1992b) among the variety of taxa on which they 
prey. In the upper elevations of the Sierra Nevada (about 1,200 to 
1,525 m (4,000 to 5,000 ft), the primary prey is the northern flying 
squirrel (Glaucomys sabrinus), which is most common in larger stands of 
mature forests (Verner et al. 1992b). In lower elevations of the Sierra 
Nevada and in southern California, the primary prey is the dusky-footed 
woodrat (Neotoma fuscipes) (Thrailkill and Bias 1989), which is most 
abundant in shrubby habitats and uncommon in pure conifer forests or 
forests with little shrub understory (Williams et al. 1992). Both 
flying squirrels and woodrats occur in the diets of owls in the central 
Sierra Nevada (Verner et al. 1992b). Home ranges of owls in areas where 
the primary prey is northern flying squirrels are consistently larger 
than those where the primary prey is dusky-footed woodrats presumably 
because woodrats occur in greater densities and weigh more than flying 
squirrels (Zabel et al. 1992a). Verner et al. (1992b) reported that 
approximately 25 percent of known owl sites in the Sierra Nevada occur 
where woodrats are the primary prey species and 75 percent of sites 
occur where flying squirrels are the primary prey species.
    Other prey items include gophers (Thomomys spp.), mice (Peromyscus 
spp.), diurnal squirrels (Tamiasciurus douglasii, Sciurus griseus, 
Spermophilus beecheyi, Eutamias spp.) and a variety of other rodents; 
shrews (Sorex spp.); moles (Scapanus spp); bats (Myotis spp.); birds; 
frogs; lizards; and insects (Verner et al. 1992b, Gutierrez et al. 
1995, Tibstra 1999). California spotted owls have low metabolic rates 
relative to other birds. Analysis of metabolic rates and the energy 
content of prey items indicates that an individual California spotted 
owl would need to eat one flying squirrel every 1.8 days or one woodrat 
every 3.7 days (Weathers et al. 2001).
    California spotted owls in the Sierra Nevada forage most commonly 
in intermediate- to late-successional forests with greater than 40 
percent canopy cover and a mixture of tree sizes, some larger than 61 
cm (24 in) in dbh. The birds consistently use stands with significantly 
greater canopy cover, total live tree basal area, basal area of 
hardwoods and conifers, snag basal area, and dead and downed wood than 
are found at random locations within the forest. Studies on the Tahoe 
and Eldorado National Forests found that owls forage in stands with 
large diameter trees (defined as trees greater than 61 cm (24 in) in 
dbh in one study and trees 51 to 89 cm (20 to 35 in) in dbh in the 
other) significantly more than expected based on availability. Owls 
also forage in stands with trees between 30 and 61 cm (12 and 24 in) 
dbh and greater than 70 percent canopy cover significantly more than 
expected, based on the proportion of that forest type (USFS 2001a).
    Stands suitable for owl foraging have: (1) At least two canopy 
layers; (2) dominant and codominant trees in the canopy averaging at 
least 28 cm (11 in) in dbh; (3) at least 40 percent canopy cover in 
overstory trees (30 percent canopy cover in red fir dominated forests); 
and (4) higher than average numbers of snags and downed woody material. 
California spotted owls forage in forests with ample open flying space 
within and beneath the canopy (Gutierrez et al. 1995); therefore, 
extremely dense stands may not be used

[[Page 7589]]

for foraging. Although canopy covers down to 40 percent are suitable 
for foraging, they appear to be so only marginally. Radio tracking data 
from the Sierra National Forest showed that owls tended to forage more 
in sites with greater than 50 percent canopy cover than predicted from 
their availability; while stands with 40 to 50 percent canopy cover 
were used about in proportion to their availability (USFS 2001a). The 
subspecies avoids open (0-30 percent canopy cover; Gutierrez et al. 
1992) or logged (Call 1990, Zabel et al. 1992b, Gutierrez and Pritchard 
1990) areas.
    Winter Habitat. Winter habitats of owls that undertake altitudinal 
migrations have similar canopy closures, but lower basal areas of both 
green trees and snags, and higher shrub densities than higher-elevation 
summer habitats (Gutierrez et al. 1995).
    General Description of Suitable Habitat. Based on the above 
studies, nesting habitat for California spotted owls is generally 
described as stands with an average dominant and co-dominant tree 
diameter of greater than 24 in and canopy cover of greater than 70 
percent. Foraging habitat is generally described as stands of trees of 
30 cm (12 in) in diameter or greater, with canopy cover of 40 percent 
or greater. Exceptions to both descriptions are known to occur. 
Suitable habitat includes California Wildlife Habitat Relationship 
(WHR) habitat types 4M, 4D, 5M, 5D, and 6 (Mayer and Laudenslayer 

Home Range

    Spotted owl pairs have large home ranges that may overlap those of 
conspecifics (Verner et al. 1992b). A portion of the home range is 
defended as a territory, especially against unknown intruders 
(Guti[eacute]rrez et al. 1995). However, territorial disputes between 
neighbors are rare. Members of the same sex are more likely to display 
aggression toward each other than members of the opposite sex (Verner 
et al. 1992b). Spotted owls may roost near conspecifics other than 
their mates (Guti[eacute]rrez et al. 1995). Verner et al. 1992b 
suggested that the spotted owl territorial system functions such that 
an individual or pair are dominant within a territory and prevent 
conspecifics from breeding there, but that feeding or roosting by those 
birds may be tolerated.
    Carey et al. (1992) studied the relationship between the amount of 
habitat used by northern spotted owls and prey abundance within those 
habitats. They found that owls used more area in habitats where the 
estimated biomass of medium sized prey, primarily flying squirrels and 
woodrats, was lower. The largest home ranges of California spotted owls 
occur where flying squirrels comprise the majority of the owl's diet 
and the smallest occur where woodrats dominate (Verner et al. 1992b, 
Zabel et al. 1992a). Woodrat populations are denser than flying 
squirrel populations, often by at least 10 fold, and woodrats weigh 
nearly twice as much as flying squirrels. Variation in prey 
availability likely affects the percentage of California spotted owl 
pairs that nest and successfully fledge young. Weather may also affect 
these parameters, either by directly affecting the owls or by affecting 
their prey base (Verner et al. 1992b).
    Estimates of California spotted owl home range size are extremely 
variable. All available data indicate that they are smallest in 
habitats at relatively low elevations that are dominated by hardwoods, 
intermediate in size in conifer forests in the central Sierra Nevada, 
and largest in the true fir forests in the northern Sierra Nevada 
(Zabel et al. 1992a, USFS 2001a). Based on an analysis of data from 
telemetry studies of California spotted owls, mean breeding season pair 
home range sizes have been estimated as 3,642 ha (9,000 ac) in true fir 
forests on the Lassen National Forest; 1,902 ha (4,700 ac) in mixed 
conifer forests on the Tahoe and Eldorado National Forests; and 1,012 
ha (2,500 ac) in mixed conifer forests on the Sierra National Forest. 
Zimmerman et al. (2000) used radiotelemetry data to estimate the 
breeding season home range of two pairs of California spotted owls in 
the San Bernardino Mountains of southern California. The average home 
range (571 ha (1,410 ac)) was smaller than those reported for the 
Sierra Nevada and varied widely between the two pairs (325 to 816 ha 
(803 to 2,016 ac)).
    Guti[eacute]rrez et al. (1992) analyzed the sizes of stands 
containing nest trees (i.e., nest stands) and the cumulative sizes of 
each nest stand plus all adjoining stands that were in vegetation 
strata preferentially used by owls for nesting. The mean size of nest 
stands was about 40 ha (100 ac); the mean size of the nest stand plus 
adjacent suitable stands was about 120 ha (300 ac). In radio tracking 
studies, the central area including half of the foraging locations of 
owls was found to vary from an average of 128 ha (317 ac) on the Sierra 
National Forest to an average of 319 ha (788 ac) on the Lassen National 
Forest (Guti[eacute]rrez et al. 1992). Bingham and Noon (1997) used 
radiotelemetry data to calculate core areas within the home ranges of 
four California spotted owls. Owls used the core areas more than would 
be expected if the entire home range were used at random. Core areas 
contained an average of 66 percent of points at which owls were located 
within an average of 21 percent of the home range.
    Habitat in Home Range. California spotted owls were found to select 
more consistently for habitat patches with high canopy cover than for 
large tree size-class (Zabel et al. 1992a). Call (1990) estimated 42 
percent of the home range to be medium timber 28 to 53 cm (11 to 21 in) 
dbh, and 55 percent large timber greater than 53 cm (21 in). The 
proportion of habitat in home ranges of owls in conifer forests of the 
Sierra Nevada with canopy cover greater than 40 percent was 68 percent 
and 81 percent for the two conifer sites studied. (Zabel et al. 1992a).
    California spotted owls have been known to use stands that were 
recently selectively harvested (Zabel et al. 1992b). However, where 
forests in the Sierra National Forest were heavily thinned, owls 
consistently nested in patches with large, old, high crown-volume trees 
(North et al. 2000), relying on the remaining components of the 
original forest.
    Numerous studies have described habitat used by spotted owls and 
habitat that occurs around owl nest sites and activity centers, but the 
relationships between these forest habitat characteristics and the 
distribution and demographic performance of California spotted owls are 
not completely understood. Several studies that have related habitat 
characteristics with California spotted owl demographic performance and 
occupancy rates found that productivity was positively correlated with 
amounts of forest with high canopy cover. Blakesley (2002a) 
characterized habitat within 1,830 ha (4,532 ac) circles surrounding 67 
California spotted owl nest sites in northeastern California and used 
those data to explain observed variation in site occupancy, apparent 
survival probability, reproductive output, and nest success. Site 
occupancy was positively associated with the amount of habitat 
dominated by large trees and high canopy cover. North et al. (2000) 
found higher reproduction in conifer forest associated with high 
foliage volumes and concluded: ``The possible interaction of weather 
and nest-site structure on owl reproduction suggests forest managers 
should be cautious about reducing canopy volume in potential owl 
nesting areas. Retaining groups of large, old, high crown-volume trees 
may be needed to maintain the number of potential nesting sites in a 
forest.'' Apparent survival and

[[Page 7590]]

reproductive output were positively correlated with the proportion of 
habitat surrounding each nest that was selected by the owls throughout 
the Sierra Nevada, as described by Guti[eacute]rrez et al. (1992). Nest 
success was positively associated with the presence of large trees 
within the nest stand.
    Verner et al. (1992b) reported that about 75 percent of the 
California spotted owls in the Sierra Nevada occurred in areas where 
the northern flying squirrel was the primary prey species. Northern 
flying squirrels have been shown to be most common in larger stands of 
mature forests (Williams et al. 1992). Flying squirrels typically use 
older mature forest because they provide suitable nest sites, including 
snags, and abundant sources of food including arboreal lichens and 
truffles, which are associated with an abundance of soil organic matter 
and decaying logs (Verner et al. 1992b). In second-growth forests in 
Oregon, northern flying squirrels were found in younger forests if 
large snags and down logs remained from earlier stands (Carey and 
Peeler 1995). Thus, past selection harvest that removed the largest 
trees and snags probably did not favor northern flying squirrels, and, 
therefore, probably had negative effects on foraging by California 
spotted owls.
    Blakesley (2002a, pers. comm. 2002) studied California spotted owls 
in an area where northern flying squirrels (Glaucomys sabrinus) 
comprised 70 to 80 percent of prey taken. She found that both survival 
and reproductive output were positively related to the proportion of 
the home range that was comprised of habitat selected by owls. 
Furthermore, site occupancy and reproductive output were negatively 
associated with the amount of non-habitat (non-forest and areas 
dominated by small trees and/or very low canopy cover).
    In areas where the primary prey consists of dusky-footed woodrats, 
effects of timber harvest, either by selection or small patch cuts, may 
have been less severe on spotted owl prey. Dusky-footed woodrats are 
more abundant in shrubby areas than in areas with little shrub 
understory (Williams et al. 1992), so this forage species may persist 
in harvested areas, at least at the lower elevations where it is more 
common. Franklin et al. (2000), who studied demographic performance of 
northern spotted owls in an area of northwestern California where 
dusky-footed woodrats were the primary prey, reported that adult owls 
with access to larger blocks of suitable forested habitat had slightly 
lower mortality rates, but those with home ranges that were more patchy 
with more openings had slightly higher fecundity (number of young 
produced per breeding female). A landscape pattern with some small 
patches of other habitats dispersed within and around a main patch of 
old forest appeared to provide the optimum balance in promoting both 
high fecundity and high survival. It seems likely that California 
spotted owls would have similar responses in the minority of their 
range where dusky-footed woodrats are the primary prey and thus may be 
less affected by habitat modification in those areas.
    According to McKelvey and Johnston (1992), clear-cutting was the 
predominant harvest method on Sierran national forests only from 1983 
through 1987. In areas where clear-cutting occurred during those years, 
and perhaps also where catastrophic fire has eliminated forested 
habitat, it may be reasonable to evaluate impacts based on studies of 
the effects of clear-cutting on the similar northern spotted owl. Bart 
(1995b) examined the relationship between amount of a northern spotted 
owl pair's home range that is suitable habitat and productivity and 
survivorship of owls. In Bart's (1995b) study area, habitat remaining 
after harvest was either of good quality (i.e., remaining old growth) 
or very poor quality unsuitable for extensive use by owls (clear cuts). 
That analysis suggested that removing any suitable habitat within the 
vicinity of the nest tends to reduce productivity and survivorship of 
resident owls. Bart concluded that replacement rate reproduction might 
occur when 30 to 50 percent suitable habitat is retained within an 
owl's home range. However, he also noted that productivity and 
survivorship declined steadily below 80 percent suitable habitat and 
advised that northern spotted owl habitat should not be reduced to 
perceived thresholds in all instances or viability could be 
compromised. The primary form of habitat modification in the Bart 
(1995b) analysis area was clear-cutting. Therefore, these results may 
only have limited application to the California spotted owl, because 
much of the range of the California spotted owl has been selectively 
harvested. The selection harvest practiced in the Sierra is believed to 
have lowered habitat quality by removing large trees and snags, but it 
may not have rendered habitat completely unsuitable (USFS 2001a). Thus, 
the degree of impact of past selection harvest practices on California 
spotted owls remains unclear.
    Spotted owl distribution in the Sierra Nevada is generally 
continuous and of uniform density within the historic range. However, 
several ``areas of concern'' were identified in Beck and Gould (1992). 
These are areas where densities of spotted owls are low, local 
populations are isolated, or distribution of habitat or owls is not 
continuous or is restricted because of past timber harvest, fire, and 
natural breaks in habitat. Areas of concern might be important if the 
range of the spotted owl begins to shrink. Beck and Gould (1992) 
identified 16 areas distributed throughout the range where there are 
gaps that delineate discontinuities in owl distribution (no habitat 
exists or there is a bottleneck) and 19 areas where concern relates to 
low population density, fragmented habitat, or loss of habitat due to 
    The USFS (2001a) further cautioned that management in at least nine 
of these areas of concern in the Sierra Nevada could have 
disproportionate impacts to spotted owls without special management 
consideration. USFS noted that areas of concern that fall within 
checkerboard ownerships (blocks of private land interspersed with 
Federal lands) or fragmented habitats warranted special attention. 
Final management direction selected by the USFS-modified alternative 8 
(USFS 2001b) included objectives for the amounts of habitat within each 
owl home range to provide for replacement rate reproduction.

Demographic Analysis

    As one of the most intensively studied birds in the United States, 
the spotted owl has been the focus of research for well over two 
decades. Many sophisticated statistical techniques for estimating 
population trends have been developed and refined using data from the 
northern spotted owl, and the state of information for the California 
subspecies has benefitted accordingly. Across the range of the 
California spotted owl, five study areas (Lassen, Eldorado, Sierra, 
Sequoia-Kings Canyon, and San Bernardino), totaling about 2,200 square 
miles, have been established to examine the subspecies' population 
status. This research serves as a valuable resource for evaluating 
whether or not listing under the ESA may be warranted. In this section, 
we offer a synopsis and evaluation of the most current research on 
California spotted owl population trends. Because analytical techniques 
for assessing population status are complex, it is necessary to discuss 
the techniques, the studies, and their conclusions in some detail.
    Several analytical methods have been applied to the analysis of 
population trend in spotted owls, and each method carries certain 
strengths and

[[Page 7591]]

weaknesses. Thus, to best understand population trend, it is important 
to concurrently assess the results of all methods instead of relying on 
a single analytical approach. One of the simpler methods uses raw 
empirical abundance data, where banded owls are counted and numbers are 
compared over time. Population trends can then be crudely assessed by 
evaluating abundance data from one year against similar data from a 
later year, or multiple years of data can be used in a regression 
analysis to determine the population trend from the slope of a 
regression line. While count data may appear straightforward, they are 
often subject to important sources of unquantifiable bias if the 
ability to detect owls changes from year to year. This can occur if 
survey effort changes over the course of the study or if the study area 
changes in size during the study period. Also, variation in 
detectability can be caused by environmental or behavioral factors. 
Numerous sources of possible bias can be present during the collection 
of abundance data in the field, especially over the long periods of 
time required to evaluate population trends in long-lived species such 
as spotted owls. However, basic abundance data can provide a reference 
point for comparison with the results of more sophisticated statistical 
methods, especially when possible error is reduced by careful data 
collection. Abundance data are available for each of the California 
spotted owl study areas, and are included in this evaluation by the 
    Because of the problems that accompany abundance data, scientists 
have developed more sophisticated methods for estimating population 
trends that can be described in statistical terms, and which allow 
various statistical tests of the estimated population trend. These 
methods derive estimates of the annual rate of population change, 
otherwise known as lambda ([lgr]), which is the fundamental measure for 
retrospective estimation of population trend. Varying analytical 
methods derive [lgr] from data on vital rates (i.e., birth and death 
rates) gathered using methods described for the northern spotted owl 
(Forsman 1983). Reproductive output is measured from direct observation 
of the number of young leaving the nest, and estimates of survival are 
obtained using mark-recapture techniques. Capture-recapture theory 
(Lebreton et al. 1992) provides the foundation for deriving a 
statistical estimate of survival and population trend. In brief, this 
is done by capturing and uniquely marking individuals, and then 
recapturing (or resighting) those same individuals in subsequent years 
(Lebreton et al. 1992). Some of the potential bias factors remain, such 
as variation in survey effort, but the recapture history for each 
marked individual serves as the basis for calculating vital rates for 
each age and gender class. After fecundity (i.e., birth rate: number of 
female young fledged per female) and survival for the population are 
statistically estimated from field sampled data, those estimates are 
used to compute the finite rate of population change, or [lgr].
    Lambda provides an estimate of two useful measures: the direction 
in population trend and the magnitude of population change (Franklin et 
al. 1996). A [lgr] value equal to 1.0 indicates a stationary 
population; less than 1.0 indicates a declining population; and greater 
than 1.0 indicates a growing population. The amount by which [lgr] 
differs from 1.0 indicates the magnitude of the trend (i.e., if [lgr] = 
1.10, the population has increased by an average of about 10 percent 
each year [1.10 to 1.0 = 0.10]). However, [lgr] is a point estimate, 
and this estimate has a measure of precision. Therefore, researchers 
often test whether [lgr] is significantly greater or less than 1.0, or 
equal to 1.0. For example, a [lgr] = 0.97 may not be statistically 
different from 1.0 at some predetermined significance level if the 
confidence interval includes 1.0 (Lande 1988).
    It should be noted that the estimate of lambda applies only to the 
period during which the data are collected. For this reason, long term 
studies are necessary to avoid misinterpretation of apparent trends. 
For instance, if a population demonstrates cycles that are completed 
over multiple decades, ten years of data may only capture a down cycle 
(which would falsely appear to be a decline) or up cycle (which would 
falsely appear to be an increase), depending on the timing of the 
    The five individual studies conducted on California spotted owl 
populations were consistent in their initial method for calculating 
[lgr], which has also been extensively described and applied in 
analyses of the northern spotted owl (Franklin et al. 1996). In this 
method, survival and fecundity estimates for females were used in a 
mathematical tool called a projection matrix to solve for [lgr]. 
Several issues may affect the validity of the projection matrix 
approach to calculating lambda. First, the method assumes that adult 
survival and fecundity are constant over time (Franklin et al. 1996). 
Long term research on the northern spotted owl has demonstrated that 
this assumption is sometimes violated. Survival rates are not constant 
(Burnham et al. 1996), and spotted owls have demonstrated variable 
annual fecundity, with occasional years of very high fecundity 
(Franklin et al. 2002). However, the magnitude of the resulting bias 
appears to be small (Burnham et al. 1996, Noon and Biles 1990). Second, 
individuals, particularly juveniles, may emigrate to areas outside the 
study area boundaries. Even though they could still be alive, these 
individuals are considered mortalities because they disappear from the 
study area, resulting in a survival rate that is biased low (Raphael 
1996). To better understand the possible error in juvenile mortality 
rates, researchers compare the observed mortality rate with calculated 
theoretical rates that would be necessary for a stable population, and 
examine the difference. Although useful in some respects, this exercise 
does not alter the estimate of lambda for the subject owl population. 
The issue of juvenile emigration was addressed in the 1999 meta-
analysis for the northern spotted owl, as well as for some of the 
individual northern spotted owl study areas, and overall trend 
estimates were adjusted for juvenile emigration (Franklin et al. 1999).
    Another potential issue regarding the projection matrix method is 
that the calculation includes only territorial birds (which are 
relatively easy to locate), ignoring nonterritorial, unlocated 
``floaters'' that may be present and available to fill vacancies left 
by the eventual mortality of breeding birds (Franklin 1992). Bart 
(1995b) argued that the presence of floaters causes population trends 
to be determined by the trend in the amount of habitat, not by birth 
and survival rates. Using lambda estimates corrected for floaters and 
false juvenile mortalities, Bart (1995b) calculated that lambda 
estimates using the projection matrix method could be 0.13 to 0.03 
lower than the actual value. Thus, for example, a population with an 
estimated lambda of 0.90 (signifying a decline of 10 percent per year) 
could actually be an increasing population. This argument should be 
considered in evaluation of lambda estimates. Trends in the 
nonterritorial segment of the population cannot be evaluated with the 
projection matrix method, although it is likely that over the long 
term, trends in the territorial and nonterritorial segments will follow 
similar trajectories, since they both depend on similar environmental 
    For these reasons, we approach the use of population matrix [lgr] 
estimates with caution in this finding, and where possible, has sought 

[[Page 7592]]

corroborative data and analyses before concluding that a population is 
declining. Our following discussion of the results from each of the 
five study areas will include evaluation of potential error in the 
lambda estimate that might result from these factors.
    More recently, the data from the five study areas were reanalyzed 
using another statistical method. In 2001, owl researchers from the 
five California spotted owl study areas, timber industry consultants, 
and stakeholders met with experts in population analyses to conduct a 
meta-analysis of the available data (Franklin et al. 2002). The term 
meta-analysis refers to the combined analysis of data collected from 
numerous studies to increase sample size and investigate relationships 
that would be difficult to assess with data from an individual study. A 
draft report authored by 15 participants (Franklin et al. 2002) 
summarized the results of the five-day meta-analysis workshop and 
subsequent analysis.
    It is our understanding that, as of the publication of this 
finding, peer review comments have been received by the authors of the 
meta-analysis, but the incorporation of peer review comments by the 
authors has not been completed. Thus, the meta-analysis manuscript 
remains a draft. We have examined the draft meta-analysis document, the 
comments of prominent peer reviewers, and solicited comments from the 
authors regarding our conclusions herein. We regard the draft meta-
analysis as the best available science on the subject, but as stated 
above, we have not relied solely on this analysis in developing our 
conclusions regarding population trend.
    The meta-analysis of adult survival was based on female and male 
adult capture histories for the five study areas, but fecundity was 
estimated for each study area separately because differences existed in 
field sampling protocols. To eliminate a possible bias in projection 
matrix estimates of [lgr] due to inaccurate rates of survival 
(resulting from unknown emigration rates), a new technique was used to 
calculate [lgr], called the ``temporal symmetry capture-recapture 
model'' (Pradel 1996). Pradel's method calculates the rate of change in 
population size between two successive years using mark-recapture 
histories for each owl, and since this technique calculates annual 
estimates, [lgr] can change each year. In contrast, the projection 
matrix method calculates an average [lgr] estimate for the period of 
study using a population's average birth and death rates. Pradel's 
measure applies to subadult and adult territorial owls, and 
incorporates birth, death, emigration, and immigration rates. Estimates 
of juvenile survival are unnecessary because movement of spotted owls 
into and out of the study area is considered in changes of owl numbers 
over time.
    While Pradel's [lgr] accounts for permanent emigration of 
juveniles, it doesn't provide insight as to the root cause of a 
population's rate of change. For example, if [lgr] = 1.0, indicating a 
stable population, it is impossible to know if the stability is a 
result of immigration or new recruits from births, which prevents 
inferences about the health of the local population (Franklin et al. 
2002). Thus, it is important that trends in survival and fecundity 
rates be examined concurrently with assessments of [lgr]. Pradel's 
[lgr] provides information as to whether owls are being replaced from 
within or outside the study area, and not solely whether they are 
replacing themselves, which is the goal of the projection matrix 
approach. Because the Pradel method provides an estimate of one [lgr] 
for each year, the annual [lgr] estimates can themselves be assessed 
for trends, and a mean estimate can be calculated for the period of 
    Franklin et al. (2002) applied the Pradel method to each of the 
five individual study areas, and conducted a combined meta-analysis of 
the results from the four study areas (Lassen, Eldorado, Sierra, and 
Sequoia / Kings Canyon) that lie in the Sierra Nevada. The following 
discussion details the results of the earlier projection matrix 
analyses and reports of basic count data for each study area, and 
compares those results with the new results derived using the Pradel 
method, as reported by the draft. Following the discussion of 
individual areas, we will describe the results of the meta-analysis of 
the four combined Sierra Nevada study areas.
    Since survey areas changed throughout the course of some studies, 
only those areas (within larger study areas) that received surveys from 
start to finish were included in the new analysis, and only years that 
received consistent survey effort were used in the analysis (Lassen 
study area [490 mi\2\]: 1992 to 2000; Eldorado study area [137 mi\2\]: 
1990 to 2000; Sierra study area [137 mi\2\]: 1990 to 2000 Sequoia and 
Kings Canyon study area [132 mi\2\]: 1991 to 2000; San Bernardino study 
area [730 mi\2\]: 1991 to 1998).
    In this review, we primarily used the most recent report or 
published article for each area, although we reference earlier reports 
to clarify apparent changes in results for a given area. We summarize 
the results below.
    Lassen Study Area--The Lassen study area encompassed approximately 
850 mi\2\ in northeastern California, the majority of which was located 
in the Lassen National Forest. Small segments of the study area 
included the Plumas National Forest, private timber lands, Lassen 
Volcanic National Park, and Bureau of Land Management land. According 
to Blakesley and Noon (in litt. 2003), four lines of evidence suggest 
that the Lassen population has been decreasing. However, this 
information, received very recently, could not be fully evaluated. The 
most recent publication for this study area (Blakesley et al. 2001) 
covered 10 years of field sampling (1990 to 1999), during which the 
annual rate of population change was estimated to be 0.910 using the 
projection matrix method. This estimate was significantly less than 
that of a stationary population ([lgr] = 1.0), and suggested that the 
territorial female owl population (those females that occupy and defend 
a habitat area) declined 9 percent annually from 1990 to 1999. 
Blakesley et al.(2001) inferred that if the conditions present during 
their study remained constant into the future, and if the true rate of 
change were as low as 4 percent instead of the estimated 9 percent, 
that the population would decline by one-half within 20 years. Such 
forecasting beyond the period of data collection is unreliable, and the 
accuracy of this projection is likely biased, as conditions are 
unlikely to remain constant for 20 years (Burnham et al. 1996, Raphael 
et al. 1996, Noon et al. 1992).
    We were unable to compare the estimated value of [lgr] to the 
observed numbers of territorial adults in this study, because the 
survey area increased over time. However, from the estimated growth 
rate of 0.910, we can conclude that over 50 percent of the population 
would be lost by the end of the study. According to Blakesley and Noon 
(in litt. 2003), within 68 territories surveyed consistently from 1993 
to 2001, the number of female owls declined from 56 to 37. This 
suggests a decline of 5 percent annually, which is not statistically 
different from the 9 percent decline estimated above. A potentially 
large source of error arises from unknown rates of juvenile and adult 
emigration. Blakesley et al. (2001) suggested that while incorrect 
juvenile emigration rates may have resulted in a survival estimate 
biased low, the magnitude of the bias was probably small. For the 
Lassen population to demonstrate a stationary trend during the study 
period (given that all other vital rates were accurate, including an

[[Page 7593]]

adult survival probability of 0.827), the juvenile survival rate would 
have to more than double (from the estimated 0.333) to 0.790. However, 
given that all other parameters remain the same, Franklin (2003) 
estimated that if adult and subadult survival was actually 0.85, 
juvenile survival would have to be 0.657 to achieve a stationary 
population, and if adult and subadult survival were actually 0.87, 
juvenile survival would have to be 0.55 for a stationary population. A 
juvenile survival probability of 0.55 is within the realm of 
possibility based on juvenile survival estimates for northern spotted 
owls on two study areas (Franklin et al. 1999).
    The meta-analysis for this study area included nine years of 
sampling (1992 to 2000) and encompassed 490 mi\2\. The mean [lgr] 
estimate for the period using Pradel's method was less than 1.0 
(0.985), but was not statistically different from that of a stationary 
population ([lgr] = 1.0). Examination of the annual [lgr] estimates 
(per year, as opposed to the above mean [lgr]) showed no evidence of a 
trend for the Lassen study, and adult apparent survival showed no 
substantive variation or trends through time. Fecundity was so variable 
through time that a linear trend (as opposed to sporadic high-low 
trends) could not be identified.
    Although there is information that suggests that this population 
may be declining, uncertainties exist when interpreting the projection 
matrix approach, actual counts, and Pradel's methodology. Without 
further refinement of the projection matrix approach (i.e., adjusting 
juvenile survival estimates using radio telemetry), it is difficult to 
reconcile the declining projection matrix [lgr] of 0.910 with the 
statistically stationary estimate of 0.985 derived using Pradel's 
methodology. Thus, we cannot conclude with certainty that the 
population is declining, increasing, or stationary.
    Eldorado Study Area--The Eldorado study area consisted of two 
segments: a 137-mi\2\ density study area, and a 220-mi\2\ regional 
study area. The most recent publication for this study area (Seamans et 
al. 2001a) covered 10 years of field sampling (1990 to 1999). Although 
surveys took place from 1986 to 1999 in the density study area, surveys 
in the regional study area were initiated in 1997. Only data from 1990 
to 1999 were used because survey effort and sample sizes increased 
dramatically after 1989 due to increased funding (Seamans et al. 
2001a). The study area was located primarily within the Eldorado 
National Forest, but portions were also located within the Tahoe 
National Forest and the Tahoe Basin Management Area. Researchers lacked 
sufficient data to calculate the juvenile survival rate on the Eldorado 
study area, so they used the survival rate from the nearby Lassen study 
area (0.333) as a surrogate. This estimate was thought to be 
optimistic, as estimates of northern spotted owl juvenile survival from 
11 study areas averaged 0.258 (Forsman 1996), and in the Eldorado study 
area, 11 of 147 individuals banded as juveniles were recaptured as 
territory holders, which would translate to a survival probability of 
0.074 (Gutierrez et al. 2001). However, there is a likelihood that the 
estimated juvenile survival of 0.258 for northern spotted owls was 
underestimated, as it was not corrected for juvenile emigration. A 
later report (Franklin et al. 1999) adjusted juvenile survival 
estimates in three northern spotted owl study areas to reflect juvenile 
emigration rates calculated from radiotelemetry data. The adjusted 
juvenile survival rates were 0.598, 0.632, and 0.366. These estimates 
represented increases of 137.2%, 41.8%, and 87.9% in juvenile survival 
estimates for each respective study area.
    Using the projection matrix approach, the annual rate of population 
change was estimated to be 0.948, which was significantly less than 
that of a stationary population. This [lgr] value suggested that the 
territorial female owl population declined 5.2 percent annually from 
1990 to 1999. In contrast, female abundance at the start (1990) and 
finish (1999) of the study was 26 and 28 individuals, respectively. 
This difference between the estimated [lgr] and the rate calculated 
from actual numbers could be attributed to immigration of individuals 
into the study area. If true, this would indicate that individuals were 
not replacing themselves, but were being replaced by recruits from 
outside the study population. Earlier estimates of [lgr] from this 
study area calculated similar trends ([lgr]= 0.947) using only 6 years 
of data (Noon et al. 1992). This six year estimate was not 
statistically less than 1.0, but the power (ability to detect 
differences) of this test was low, so the trend of the population was 
uncertain at the time (Verner et al. 1992). Results from the 2001 study 
(Seamans et al. 2001a) expanded the sample size and study period, and 
increased the statistical power of their test so that their estimate of 
lambda (0.948) was then found to be statistically less than 1.0.
    The use of a surrogate juvenile survival rate in this study may 
introduce bias into the estimate of [lgr] for two reasons: the Lassen 
estimate of juvenile survival probably carries certain biases given the 
inability to consider juvenile emigration in the estimate of juvenile 
survival, and the Lassen study area may not accurately represent the 
Eldorado study area. Further, Guti[eacute]rrez et al. (2001) reports 
that survey effort for this study area changed over time, and that 
survey effort can influence density and survival estimates. For this 
reason, data from the first four years of study were not included in 
the estimate of survival or reproduction (Seamans et al. 2001a analyzed 
data starting in 1990, not 1986). In a subsequent report (Seamans et 
al. 2001b), the projection matrix estimate of [lgr] was compared to a 
growth rate calculated from actual numbers of adult females present 
during the study. The growth estimate from actual numbers was 0.951, 
and was significantly less than zero. This estimate was calculated 
using data from 1993 (37 adult females) to 2000 (24 adult females), 
while the value derived from the projection matrix approach (0.948), 
which was calculated using data from 1990 to 1999.
    The meta-analysis for this study area included 11 years of sampling 
(1990 to 2000) and encompassed 137 mi\2\. The mean [lgr] estimate for 
this study area was greater than 1.0 (1.042), and was not statistically 
different from that of a stationary population ([lgr] = 1.0). 
Examination of annual [lgr] estimates showed a significant decline, and 
similar to the Lassen study area, adult apparent survival showed no 
substantive variation or trends through time. No linear trend in 
fecundity could be identified.
    While the projection matrix estimate of [lgr] showed a decline, 
(and trend in Pradel's annual [lgr] showed a decline), actual counts 
increased a small amount from 1990 (26 adult females) to 1999 (28 adult 
females) but decreased from 1993 (37 adult females) to 2000 (24 adult 

females), and the mean [lgr] estimate using Pradel's method appeared to 
show a stationary population. Furthermore, there were substantive 
uncertainties regarding the accuracy of vital rate estimates used in 
the projection matrix estimate of [lgr]. These results do not allow us 
to reach a definitive decision with respect to population trend on the 
Eldorado study area, and we cannot conclude the population is 
    Sierra Study Area--The Sierra study area was located primarily (92 
percent) within the Sierra National Forest, and encompassed the 
watersheds of the San Joaquin River and the North Fork of the Kings 
River (Franklin et al. 2002). The study area included approximately 263 
mi\2\, and the boundaries were delineated based on National Forest 
boundaries and major topographic features such as

[[Page 7594]]

ridges and drainages. Spotted owl telemetry studies and intensive 
surveys began in 1987 and 1990, respectively, on a 160 mi\2\ portion of 
this study area (old Sierra study area). In 1994, surveys were expanded 
to include an additional 103 mi\2\ (new Sierra study area; Steger et 
al. 1999). Juvenile survival rate was not calculated using data from 
this study area. Instead, the juvenile survival rate from the San 
Bernardino study area (0.328) was used to approximate the Sierra study 
area's juvenile survival rate.
    Using survey data from 1990 to 2000 and the projection matrix 

method, the annual rate of population change was estimated for the old 
Sierra study area (1987 to 2000) and both old and new Sierra study 
areas combined (1987 to 2000). Annual rates of population change for 
the old Sierra and combined Sierra study areas were 0.897 and 0.901, 
respectively. These estimates were significantly less than that of a 
stationary population, and suggested that the territorial female owl 
population declined about 10 percent annually from 1987 to 2000. For an 
11 year period (1990 to 2000), this translates to a population decline 
of around 60 percent. For the old Sierra study area during 1991 to 2000 
(1990 was not examined as survey guidelines were not yet established on 
the study area), actual owl numbers seemed to corroborate a decline, 
albeit the drop in numbers was less severe than 60 percent. Owl 
abundance in 1991 and 2000 were 69 and 55, respectively. These numbers 
represent a 20 percent decrease, although the accuracy of the count 
numbers is unknown. The new Sierra study area also showed a decline: 
actual owl numbers dropped from 37 in 1994 to 29 in 2000.
    The meta-analysis for this study area included 11 years of sampling 
(1990 to 2000) and encompassed 137 mi\2\. The mean [lgr] estimate for 
this study area was less than 1.0 (0.961), but was not statistically 
different from that of a stationary population ([lgr] = 1.0). Annual 
[lgr] estimates showed a weak (nonsignificant) decline, and adult 
apparent survival showed no substantive variation or trends through 
time. The Sierra study showed a negative trend in fecundity, which 
could have been driven by a high reproduction year early in the study.
    Although the mean [lgr] was statistically stationary using Pradel's 
methodology, actual numbers of owls declined; the projection matrix 
approach showed a decline; there was a negative trend in fecundity; and 
there was a weak, nonsignificant decline in annual [lgr] estimates 
(using Pradel's method). It appears that a decline in this study area 
is possible, but the use of a surrogate juvenile survival rate 
introduced a bias of unknown proportion, and thus, the magnitude of a 
possible decline remains uncertain.
    Sequoia and Kings Canyon Study Area--The Sequoia and Kings Canyon 
study area encompassed approximately 130 mi\2\ of land in Fresno and 
Tulare counties. The majority of the area was located in the Sequoia 
and Kings Canyon National Parks. Small segments of the study area 
include the Kings River watershed, but most of the study area was in 
the Kaweah River watershed (Franklin et al. 2002). Surveys in this 
study area cover 11 years of field sampling (1990 to 2000), but useful 
data exist from a previous demographic study that began in 1988 (Steger 
et al. 2000). Demographic surveys were conducted on130 mi\2\ of land in 
this area, and methods for calculating [lgr] were identical to those 
used for the Sierra study area. The annual rate of population growth 
using the projection matrix method was estimated to be 0.973, 
suggesting a decline of 2.7 percent per year. Statistical testing found 
that [lgr] was not significantly less than 1.0. Actual owl counts 
during the study period seemed to indicate that the population might be 
growing, but again, the accuracy of such numbers is uncertain. Owl 
abundance in 1990 and 2000 were 54 and 64, respectively.
    The meta-analysis for the Sequoia and Kings Canyon study area 
covered 132 mi\2\ during 1991 to 2000. The resulting mean [lgr] 
estimate was 0.984, but was not statistically different from that of a 
stationary population. A significant quadratic trend (decline, then 
increase) was detected for annual [lgr] estimates, but adult apparent 
survival showed no substantive variation or trends through time. A 
linear trend could not be identified in fecundity estimates, as 
fecundity was highly variable through time. Apparent survival for the 
Sequoia and Kings Canyon study area was significantly higher (0.877) 
than that of the other study areas combined (0.819).
    Lambda estimates using the projection matrix approach and Pradel's 
method suggest stationary population trends, and actual owl numbers do 
not show declines. Trend in annual [lgr] estimates also does not show a 
decline, and apparent survival in this study area was higher than all 
other study areas examined in this finding. Based on these results, and 
considering the inclusion of the juvenile survival rate from another 
study area, we cannot conclude that this population is declining.
    San Bernardino Study Area--The San Bernardino study area was 
located entirely within the San Bernardino National Forest, and 
comprised all suitable habitat for spotted owls within the mountains. 
Surveys covering approximately 200 mi\2\ (Big Bear study area) began in 
1987, but were expanded in 1989 to cover the entire San Bernardino 
Mountain range (approximately 730 mi\2\; San Bernardino Mountains study 
area; Guti[eacute]rrez et al 1999). This study area was unique in that 
it exists in southern California as a relatively isolated population 
(Guti[eacute]rrez and Pritchard 1990, LaHaye et al.1994). Higher 
elevations in the study area contained forested habitat suitable for 
spotted owls, while lowland areas of unsuitable desert scrub and 
chaparral habitats surrounded and isolated the higher peaks (Noon and 
McKelvey 1992). Early projection matrix studies using four, five, and 
six years of data estimated significant annual declines during years 
between 1987 and 1993 ([lgr] = 0.769, 0.827 and 0.860, respectively; 
LaHaye et al. 1992, Noon et al. 1992, LaHaye et al. 1994). The annual 
rate of population change for the most recent report we possess was 
estimated to be 0.91 based on 11 years of data (1988 to 1998; LaHaye et 
al. 1999). This estimate was significantly less than that of a 
stationary population, and suggested that the territorial female owl 
population declined nine percent annually from 1988 to 1998. Over the 
11-year study period, this rate of decline would translate to a loss of 
over 60 percent of the population.
    Although all forested habitat within the San Bernardino Mountains 
study area (including unoccupied habitat) was surveyed 
(Guti[eacute]rrez 2001), survey effort increased during the study 
period. In 1989, 532 total surveys were conducted, whereas in 1998, 
1,185 total surveys were conducted (LaHaye et al. 1999). This change in 
survey effort could cause the number of owls observed in any year to be 
a function of the survey effort instead of an actual trend in numbers. 
Thus, there is a high likelihood that an assessment of actual owl 
numbers through time could be biased, and may not accurately represent 
the true population size in any given year.
    The meta-analysis for this study area included 8 years of sampling 
(1991 to 1998) and encompassed 730 mi\2\. The mean [lgr] estimate for 
this study area was less than 1.0 (0.978), but was not statistically 
different from that of a stationary population ([lgr] = 1.0). 
Examination of annual [lgr] estimates showed a weak (nonsignificant) 
decline, and as with all other study areas, adult apparent survival 
showed no

[[Page 7595]]

substantive variation or trends through time. No linear trend in 
fecundity could be identified.
    Although the projection matrix approach showed a decline and there 
was a weak, nonsignificant decline in annual [lgr] estimates using 
Pradel's method, the mean [lgr] was statistically stationary using 
Pradel's methodology. This is more meaningful than with the other study 
areas. Recall that using Pradel's method, the population could appear 
stationary or growing, even if the population growth is caused by 
outside immigration. For this study area, recruitment cannot likely be 
attributed to immigrants entering the study area, as the study area is 
relatively isolated. Thus, the disparity between the projection matrix 
estimate and the estimate using Pradel's method could be a result of 
either (1) measurement error in survival rates of juveniles or adults, 
or (2) the presence of unlocated floaters in the study area (Franklin 
1992). Regardless, we have insufficient certainty as to the status of 
this population to conclude that it is either declining, increasing, or 

Meta-Analysis Results

    The meta-analysis used the Pradel method to evaluate data from 
various study areas, as described above. The analysis was also applied 
to some aspects of the population as a whole. The estimated mean lambda 
for each of the individual studies was not significantly different than 
1.0 over the periods analyzed. The meta-analysis did not estimate a 
mean overall value of lambda for all study areas combined. Examination 
of trends in annual [lgr] over the periods analyzed for each study area 
showed no evidence of a trend for the Lassen study, a significant 
decline for the Eldorado study, a significant quadratic trend (decline, 
then increase) for the Sequoia and Kings Canyon study, and a weak 
(nonsignificant) decline for the Sierra study. The overall trend in 
annual lambda rates for these four Sierra Nevada study areas was 
declining, then increasing. The trend in annual rates for the San 
Bernardino study was a weak (nonsignificant) decline for the period 
    Adult survival rate for the Lassen, San Bernardino, Sierra, and 
Eldorado study areas combined was 0.819, which was substantially lower 
than the mean estimate (0.850) for adult northern spotted owls across 
15 study areas (Franklin et al. 1999). Except for the Sierra study 
area, fecundity estimates for the California spotted owl study areas 
were so variable through time that linear trends could not be 
identified. The Sierra study showed a negative trend in fecundity, 
which could have been driven by a high reproduction year early in the 
    Conclusions--In total, the findings reported above are not 
conclusive with respect to the population status of the California 
spotted owl. There is no definitive evidence that the population is 
decreasing across its range, and various analytical results of the 
individual study areas are not wholly supportive of conclusions 
regarding declines in any given study area. Low levels of declines may 
be occurring in some study areas, but if so, they are not clearly 
evident using existing analytical techniques. The strongest support for 
a possible decline is on the Sierra study area, and the strongest 
support for a possible stationary population is on the Sequoia and 
Kings Canyon study area. The combined rate of adult survival for all 
study areas except the Sequoia and Kings Canyon study area may be of 
concern, as it is substantially lower than that reported for the 
northern spotted owl. However, Pradel's [lgr] estimate for each study 
area consistently showed statistically stationary populations, so we 
cannot conclude that this lower adult survival rate is causing a 
decline in California spotted owl populations. At this time we have no 
clear statistical evidence to show that the California spotted owl is 
declining throughout its range.

Summary of Factors Affecting the Species

    Section 4 of the Act (16 U.S.C. 1531 et seq.) and the regulations 
(50 CFR part 424) that implement the listing provisions of the Act set 
forth the procedures for adding species to the Federal lists. A species 
may be determined to be an endangered or threatened species due to one 
or more of the five factors described in section 4(a)(1). These factors 
and their application to the California spotted owl are as follows:

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

    There are two categories of possible threats to the California 
spotted owl that are related to habitat. The first is the current 
threat related to the condition of existing populations and habitat, 
and existing, ongoing habitat modification. The second is the potential 
threat that may result from future management of habitat.
    Threats related to current condition of populations and habitat. 
Numerous authors have expressed concern over the current status of the 
California spotted owl, and much of this concern is related to the 
quality of the habitat available to the subspecies at the present time. 
The best scientific information available indicates that high survival 
of spotted owls is achieved by maintaining large, unfragmented areas of 
suitable habitat (Moen and Guti[eacute]rrez 1997, Franklin et al. 2000, 
Blakesley in litt., 2002a). Important habitat components, especially 
large trees, large snags, and large down logs, are currently in short 
supply across the range of the California spotted owl (Verner et al. 
1992b, USFS 2001a). The diameter of nest trees selected by owls in the 
Sierra Nevada is significantly greater than the average diameters of 
conifers in the Sierra Nevada. Large trees become future large snags 
and large downed logs, the latter providing important habitat 
attributes for some prey species. The length of time required to 
recover old trees and increase their density over the landscape raises 
the level of concern associated with their decline (USFS 2001a).
    Concern has been exacerbated because, although harvest volume was 
declining markedly in the 1990s, existing management direction did not 
appear to be sufficient to arrest completely habitat decline (USFS 
2001a), and because, until recently, most of the remaining old growth 
in national forests in the Sierra Nevada remained in areas available 
for timber harvest (Franklin and Fites-Kaufmann 1996, Beardsley et al. 
1999). Thus, Blakesley and Noon (1999) argued that the most positive 
step that can be taken to reverse apparent declines of California 
spotted owls would be to increase retention and recruitment of large 
trees and closed canopy conditions throughout the Sierra Nevada.
    Concern also exists because the existing habitat used by California 
spotted owls appears to be vulnerable to stand-replacing catastrophic 
fire. Removal of large overstory trees in conjunction with fire 
exclusion has lead to changes in forest structure that favor spread of 
high intensity fire. Conifer stands have become denser and composed 
mainly of trees in small and medium size classes (University of 
California 1996). The species composition of these forests has also 
shifted, from more shade intolerant, fire-hardy species such as 
ponderosa pine and black oaks to more shade tolerant, fire sensitive 
species such as white fir and incense-cedar (Verner et al. 1992, 
Weatherspoon et al. 1992). Similar increases in density and changes in 
species composition have been documented for coniferous forests of 
southern California (Weatherspoon et al. 1992, Minnich et al. 1995). 
Forests in

[[Page 7596]]

southern California were logged significantly into the 1960s (Verner et 
al. 1992a) and have also been affected by intensive fire suppression. 
Dense stand conditions in California forests have lead to increased 
tree mortality, due to competition, drought, insects, disease, and, in 
some cases, air pollution (University of California 1996). The 
increased density and continuity of young trees together with increased 
fuels from fire suppression and tree mortality have created conditions 
favorable to more intense and severe fires (University of California 
1996). Over the last 30 years, the annual acreage burned in the Sierra 
has been about 19,020 ha (47,000 ac), but in the last ten years, that 
average was 30,756 ha (76,000 ac) (USFS 2001b).
    Paradoxically, the growth of understory trees that contribute to 
the high degree of canopy closure favored by California spotted owls 
also increases the risk that wildfire might spread into the canopy and 
destroy the stand. Because fire suppression has increased density of 
stands in the Sierra Nevada, the possibility exists that it has led to 
net improvement in owl habitat in some areas (Weatherspoon et al. 1992) 
with resultant increases in spotted owls (Verner et al. 1992a). 
Weatherspoon et al. (1992) characterized forests selected by spotted 
owls as having the structural components favorable for crown fires.
    However, in recent years, relatively few California spotted owl 
sites have been severely impacted by wildfire (USFS 2001a). From 1993 
to 1998, only 15 Protected Activity Centers, a 121 ha (300 ac) 
management area established around all Forest Service owl sites in 
1993, burned in wildfires, and three of those remain occupied (USFS 
2001a). This possibly is because of the success of initial attacks on 
wildfires in Sierran mixed conifer types (Weatherspoon et al. 1992) or 
because California spotted owls often occupy relatively moist areas 
such as northern aspects (Gould 1977, Barrows 1981, Guti[eacute]rrez et 
al. 1992, North et al. 2000), lower slopes of canyons (Gould 1977, 
Guti[eacute]rrez et al. 1992), or areas close to water (Gould 1977) 
where average fire intervals are longer (Weatherspoon et al. 1992). 
Weatherspoon et al. (1992) noted that most of the large fires in the 
Sierra Nevada had occurred on the eastside and at low elevations on the 
westside, outside the areas where spotted owls occur.
    During development of the SNFPA, the overall concerns regarding the 
status of the California spotted owl and its old forest habitat were so 
pervasive that the Forest Service, the primary land manager in the 
Sierra Nevada, formally adopted the assumption that the owl's 
population was declining as a basic tenet driving land management 
direction, and in the SNFPA Record of Decision established that ``The 
primary objective is to conserve rare and likely important components 
of the landscape such as stands of mid and late seral forests with 
large tree, structural diversity and complexity, and moderate to high 
canopy cover'' (USFS 2001b).
    The SNFPA FEIS (USFS 2001a) provided analysis that suggested that 
many California spotted owl territories might not contain sufficient 
amounts of suitable habitat to provide for desirable levels of 
reproduction, based on inferences made from the work by Hunsaker et al. 
(2002) (which was in press at the time of publication of the FEIS). 
However, during the process of publication of that study, analysis of 
the data by another Forest Service scientist found that the statistical 
methodology of Hunsaker et al. (2002) was flawed and that the study's 
conclusion regarding the relationship between habitat and reproductive 
success could not be supported (Lee 2001). Thus, while the FEIS 
analysis of the amounts of habitat in home ranges may be of descriptive 
value, certain of its conclusions as to the possible population 
implications were not valid. The FEIS reported that, overall, 50 
percent of the home ranges contained less than 60 percent of their area 
in suitable habitat. In the central Sierra Nevada (represented as the 
Plumas, Tahoe, Eldorado, and Stanislaus National Forests, which contain 
about 46 percent of the owl sites in the Sierra), 58 percent of the 
home ranges contained less than 60 percent suitable habitat.
    In southern California, recent prolonged drought, particularly on 
the San Bernardino National Forest, has led to significant mortality in 
the big-cone Douglas-fir and mixed conifer vegetation types, both of 
which provide nesting, roosting, and foraging habitat for California 
spotted owls. The extent of mortality is projected to be 8,094 to 
12,140 ha (20,000 to 30,000 ac), much of which is considered suitable 
nesting/roosting habitat. The San Jacinto Mountains are experiencing 
especially high mortality. It is anticipated that most of the nesting 
and roosting habitat in the San Jacinto Mountains will be lost. This 
area supports about 10 pairs of spotted owls, all of which could be 
lost (Loe in press 2002).
    Despite well-founded concerns regarding the current status of the 
subspecies, there are several factors that suggest that the California 
spotted owl is not in immediate danger of extinction nor will be in the 
foreseeable future. These factors include: (1) The subspecies remains 
widespread and well-distributed throughout its historic range, despite 
extensive historical effects on habitat and apparent sub-optimal 
conditions in current habitat; (2) The estimated numbers of the 
subspecies combined with its wide distribution reduce the likelihood of 
widespread extirpation due to a catastrophic event; and (3) Although 
there are analyses that suggest populations may be declining, the 
population declines are not conclusively demonstrable.
    Threats to Habitat from Future Timber Harvest, Catastrophic Fire, 
and Vegetative Management. With the current status and performance of 
California spotted owl populations and their habitat in question, the 
evaluation of potential future threats is a key aspect of this finding. 
In the following discussion, we evaluate the potential effects of 
impending management on the habitat of the subspecies.
    In this evaluation, we confine the scope of our judgement of the 
future actions and programs of Federal land management agencies to 
reasonably foreseeable outcomes of established management direction, 
rather than more speculative assessment of possible future management 
scenarios. In particular, and most importantly, this limitation 
confines us to evaluation of the established management direction for 
Forest Service lands in the Sierra Nevada, (i.e., SNFPA). As discussed 
below, we are aware that Forest Service is considering changes in 
management direction, and that other parties have called for actions 
that could have more widespread impacts on California spotted owl 
habitat. However, because such proposals are not incorporated in 
established management direction, they remain outside the scope of this 
    Timber harvest on Federal lands in the Sierra Nevada--Timber 
harvest in coming decades on Forest Service lands in the Sierra Nevada 
will be governed by the Record of Decision for the SNFPA. The Record of 
Decision states: ``For each national forest affected by this decision, 
a revised allowable sale quantity (ASQ) will be established at the time 
of their Forest Plan Revision. Until those revisions are complete, the 
total annual Probable Sales Quantity (PSQ) green volume for the 11 
national forests is estimated to be approximately 191 million board 
feet (mmbf) for the next five years, which includes approximately 137 
mmbf from the pilot project for the Herger-Feinstein Quincy Library 
Group (HFQLG). The estimated annual volume for the ensuing five years 
is approximately 108 mmbf. An

[[Page 7597]]

additional 91 mmbf of salvage harvest per year may also be made 
available (USFS 2001b).
    Totaling approximately 282 mmbf per year in combined volume of 
green and salvage timber harvest for the first five years, this harvest 
level would be similar to the annual average harvest volume (about 279 
mmbf) from Sierra Nevada national forests from FY 1998 to 2000, 
described above. However, the harvest would be distributed somewhat 
differently than in past years, as over 70 percent of the green tree 
volume will be harvested from the three forests (Lassen, Plumas, and 
Tahoe) involved in the HFQLG pilot project. (Since 1994, the amount 
harvested from these three forests has ranged from 56 percent to 71 
percent of the total harvested from all Sierra forests.) All of the 
planned harvest would be subject to the SNFPA Standards and Guidelines 
summarized below. It should be noted that even though the projected 
volume from the HFQLG pilot project was 139 mmbf per year, the total 
harvest in the first two years was only about 60 mmbf, primarily as a 
result of the constraints of the SNFPA and planning delays (Mary 
Carroll-Martin, USFS, pers. comm. 2003).
    Timber harvest on private lands in the Sierra Nevada--Private 
timber harvest is widespread in the Sierra Nevada. Between 1999 and 
2001, 765 timber harvest plans covering 86,685 ha (216,675 ac) within 
the range of the California spotted owl were submitted (Susan Britting, 
Sierra Nevada Forest Protection Campaign, in litt. 2002). For the 
foreseeable future, timber harvest on industrial timber lands in the 
Sierra Nevada will be conducted in compliance with the California 
Forest Practice Rules. Regulatory aspects of the Sustained Yield Plans 
(SYP) program are further described in Factor D below.
    The primary private industrial timberland owner in the Sierra 
Nevada is Sierra Pacific Industries, Inc. (SPI), which owns about 
376,351 ha (930,000 ac) within the range of the California spotted owl. 
For the next several decades, SPI's timber harvest will be conducted 
according to their Maximum Sustainable Production (MSP) plan pursuant 
to the California Forest Practice Rules (further described in Factor D 
below). Under this plan, SPI projects an increase of large tree/closed 
canopy conditions from about 20 percent of the landscape in year one 
(current condition) to 65 percent in year 80 and stabilizing to 55 
percent in year 100. Over the 100 year period, the average diameter of 
trees increases from 18 in class (current condition) to 32 in class, 
and projections anticipate maintenance of the higher proportion of 
larger tree class over time with harvest practices (SPI 1999 a and b).
    Timber harvest in southern California--The four southern California 
National Forests are currently operating under Forest Land and Resource 
Management Plans that were completed in the late 1980s. As discussed 
further in Factor D, these plans are in the process of revision. There 
is not an Allowable Sale Quantity or Proposed Sale Quantity proposed in 
the Southern California Conservation Strategy. The prolonged mortality 
of vegetation has resulted in significant build-up of fuels in the San 
Bernardino National Forest. In order to reduce both a fuel hazard and 
risk of fire, the San Bernardino National Forest has a number of 
salvage harvest timber sales currently under contract. Additional sales 
are being planned and the sale program will respond to continuing and 
projected mortality (M. Gertsch, USFS, pers. comm. 2002). Timber 
harvest on these forests will be conducted with California spotted owl 
protection measures (M. Gertsch, USFS, pers. comm. 2002).
    In summary, available information suggests that U.S. Forest Service 
timber harvest levels in the Sierra Nevada and southern California are 
not expected to increase substantially above current levels. In 
addition, the SPI MSP is expected to provide an increasing amount of 
habitat on that large industrial ownership over the next few decades. 
Other private lands have not been specifically evaluated, but will be 
governed under the FPRs, further described below.
    Risk of Catastrophic Fire--Weatherspoon et al. (1992) identified 
the following major factors of concern in habitats of California 
spotted owls in the Sierra Nevada that pertained to fire risk: (1) 
Ingrowth of shade-tolerant tree species, creating unnaturally dense 
stands with ground-to-crown fuel ladders; (2) excessive accumulation of 
surface fuels; and (3) change in composition of tree species from fewer 
pines and black oaks to more firs and incense-cedar. Such conditions 
create a tendency towards crown fires that kill most or all trees in an 
area, which may result in direct mortality of California spotted owls 
or make the burned habitat unsuitable for the species.
    Approximately 39 percent of the California spotted owl sites on 
national forest lands in the Sierra Nevada occur in areas with high 
fire hazard risk (USFS 2001a). However, as stated above, the actual 
loss of owl sites to wildfire has been small in recent years, perhaps 
due to effective suppression and environmental factors. The annual rate 
of loss has been only 0.2 percent of the known national forest owl 
sites in the Sierra (Service 2001). Thus, based on recent rates of loss 
to catastrophic fire, it could be argued that the risk to the 
subspecies is not particularly high. Effects at some local levels have 
been larger; the Plumas National Forest lost 5 percent of protected 
activity centers (PAC, protected owl nest and surrounding habitat) per 
year over a recent two-year period (USFS 2001a). It is also argued that 
the steadily increasing amount of forest fuel creates an ever-
increasing risk of large catastrophic fires (Weatherspoon et al. 1992).
    The Forest Service currently believes that wildfire effects, 
particularly those associated with large, stand replacing wildfires, 
are a major source of risk to spotted owl populations (USFS 2001b). 
This is based on analysis of recent trends in fire occurrence and on 
the explicit assumption that the recently-observed high rate of large 
severe fires will continue. Also, the growing concern over the 
potential for disastrous wildfire effects on human communities has 
strongly influenced management direction toward reducing fuels in 
forests in proximity to human communities in the so-called Wildland 
Urban Interface (WUI). Response to this concern is manifested in 
nationwide activities under the National Fire Plan (National 
Interagency Fire Center (NIFC) 2002), which established general 
guidance and funding for land management agencies and communities 
involved in fire suppression and fuels reduction.
    This recently increased focus on reduction of forest fuels has 
substantial implications for the California spotted owl, and raises 
difficult questions about the potential benefits and risks to the 
subspecies that may result from reduction of forest fuels. In general 
terms, the situation may be described as follows: In today's forests, 
the high canopy-cover stands currently much-used by spotted owls are 
largely a product of sustained fire suppression in stands regenerating 
after high levels of harvest that occurred several decades ago. The 
large numbers of small and medium-sized understory trees that create 
high degrees of canopy cover also act as a potential fuel ladder that 

can carry fire into the forest crown, where, under some conditions, the 
fire can spread rapidly and create extensive tree mortality. The 
competition among many small trees suppresses the rate of growth of the 
stand into the larger trees that are an important component of high 
quality habitat for owl nesting and forage

[[Page 7598]]

production. More mature habitat features a high degree of foliage 
volume and canopy cover that begins high above the ground and is not as 
vulnerable to fire. Thus, the primary technique of fuels reduction, 
thinning understory trees with mechanical equipment and/or prescribed 
fire, may have detrimental effects on owl habitat in the short term (10 
to 20 years), but may favor development of habitat in the longer term, 
and may reduce the likelihood of catastrophic fire that could 
substantially degrade or eliminate habitat.
    Tradeoffs between owl habitat lost through treatments versus 
projected losses to wildfire events are complex and difficult to 
assess. The effects of vegetation treatments upon owl habitat are 
mostly immediate and relatively easy to quantify, but reductions in the 
acreage and intensity of future wildfires due to vegetation treatments 
will be realized over much longer periods. In addition, due to the 
random nature of wildfire events, projections regarding future wildfire 
have greater amounts of uncertainty and are heavily dependent upon 
assumptions that are difficult to quantify.
    In the Record of Decision for the SNFPA, the Regional Forester 
stated ``Two factors of greatest concern to me are: (1) Ensuring the 
long term protection and recovery of old forest conditions and the 
spotted owl and other species (2) being able to ensure that the risk of 
wildfires within the Sierra Nevada can be managed to protect 
ecosystems, property and communities' (USFS 2001b). The objective of 
the SNFPA's conservation strategy for California spotted owls was to 
provide the environmental conditions needed to establish a high 
likelihood of maintaining viable populations of the California spotted 
owl, well distributed across the national forests within the Sierra 
Nevada planning area. This strategy sought to maintain habitat capable 
of supporting existing owl populations, stabilize current population 
declines, and provide increases in owl habitat over time. It was based 
on providing and improving fundamental components of spotted owl 
habitat such as: a high foliage volume and complex vegetation structure 
at nest sites; a high percentage of home ranges in forests with 
moderate to high cover that are concentrated near nest sites; and 
habitat for primary prey species, especially the northern flying 
    This objective is to be accomplished through a multi-scale 
landscape strategy to: (1) Protect and manage allocations called ``Old 
Forest Emphasis Areas'' to provide large area reserves of high quality 
spotted owl habitat; (2) conduct surveys for owls where vegetation 
treatments would occur; (3) establish PACs comprising known and 
suspected nest stands and the best available 121 ha (300 ac) of habitat 
around owl activity centers; (4) establish limited operating periods 
within approximately 0.4 km (0.25 mi) of California spotted owl nest 
sites during the breeding season (March 1 through August 31); (5) 
protect and manage individual spotted owl home range core areas (972 ha 
(2,400 ac) on the Hat Creek and Eagle Lake Ranger Districts of the 
Lassen National Forest; 405 ha (1,000 ac) on the Almanor Ranger 
District of the Lassen National Forest, Modoc, Inyo, Plumas, Tahoe, 
Eldorado, Lake Tahoe Basin Management Unit, and portions of the 
Humboldt-Toiyabe and Stanislaus National Forests; and 243 ha (600 ac) 
on the Sequoia and Sierra National Forests) in the ``general forest'' 
forested areas outside of Old Forest Emphasis Areas; (6) manage the 
general forest outside of owl core areas to maintain and increase the 
amount of suitable spotted owl habitat; and (7) address fire hazard and 
risk by reducing surface and ladder fuels within strategically placed 
area treatments focusing on the urban wildland intermix zone and Old 
Forest Emphasis Areas of high hazard and risk (USFS 2001a and b).
    Based on the explicit assumption that the California spotted owl 
was in some degree of population decline, the SNFPA incorporated 
numerous Land Allocations and Standards and Guidelines (S and Gs) that 
protect existing owl habitat across the landscape and in the course of 
implementation of fuels treatments. In general, these measures apply to 
four landscape level designations. In order of increasing intensity of 
potential fuels treatment, these designations are old forest emphasis 
areas, general forest, the urban threat zone, and the urban Defense 
zone. The most important features of the S and Gs that relate to 
conservation of California spotted owls are summarized below, based on 
discussion in the SNFPA Record of Decision (USFS 2001b). More detail is 
given in the FEIS (USFS 2001a).
    Important aspects of the SNFPA allocations and S and Gs include the 
    (1) In forests west of the Sierra crest (westside), all live 
conifer trees with a dbh of 76 cm (30 in) or greater will be retained. 
East of the crest, where trees generally do not grow as large or as 
rapidly, all trees 61 cm (24 in) or greater in the eastside pine forest 
type will be retained. Montane hardwoods with a dbh of 30 cm (12 in) or 
greater within westside forest types will be retained. Prescribed burn 
prescriptions and techniques will be designed to minimize the loss of 
large trees and down material. The largest down logs will be retained 
for coarse woody debris outside of the Defense zone of the urban 
wildland intermix. Forested stands over 2 ha (5 ac) with the largest 
trees will be maintained to perpetuate their current conditions. 
Generally, in these stands no trees greater than 30 cm (12 in) dbh will 
be removed and canopy cover will not be reduced more than 10 percent 
below current conditions when applying necessary fuels reduction 
    (2) Spotted owl PACs will be applied in all designations except the 
Defense zone of the urban wildland intermix. PACS are to include at 
least 121 ha (300 ac) of the best available habitat. Total acreage in 
spotted owls PACs (including non-habitat acreage within the PACs as 
presently designated) is currently estimated at 243,258 ha (601,116 
acres) (K. Barber, USFS, pers. comm. 2003), which is about 12 percent 
of the forested acreage on national forest lands in the Sierras. Stand-
altering activities in spotted owl PACs will be limited to reduction of 
surface and ladder fuels through prescribed fire treatments. Prior to 
prescribed burning, known nest trees and trees in the immediate 
vicinity will be protected by hand line construction, tree pruning, and 
cutting of small trees within a surrounding 0.4 to 0.8 ha (one to two 
ac) area. Activities that could disturb nesting would be prohibited 
within 402 meters (0.25 mi) of nests within the breeding season unless 
it is demonstrated that nesting is not occurring. Vegetation treatments 
will occur in no more than 5 percent per year and no more than 10 
percent per decade of the California spotted owl PACs.
    (3) Spotted owl home range core areas will be applied around all 
PACs, except in the Threat zone as described below. Generally, fuel 
treatments in home range core areas will be limited to prescribed fire 
or low intensity mechanical treatments for the removal of material 
necessary to reduce surface and ladder fuels sufficient to achieve an 
average flame length of 2 m (6 ft) or less if the stand were to burn 
under 90th percentile fire weather conditions. Fuels treatment measures 
will be similar to those described in the following discussion of Old 
Forest Emphasis Areas (USFS 2001a and b).
    (4) Old Forest Emphasis Areas will be established, totaling over 
1,618,712 ha (4,000,000 ac). Currently, about 70 percent of the acreage 
in these areas is suitable owl habitat (USFS 2001a and b); thus, about 
65 percent of the

[[Page 7599]]

estimated 1.7 million ha (4.3 million ac) of existing habitat on 
national forests in the Sierras is within the Old Forest Emphasis 
Areas. About 49 percent of the California spotted owl sites known on 
national forest lands in the Sierras lie within old forest emphasis and 
wilderness areas. Additionally, all stands of high quality habitat 
outside old forest emphasis areas (i.e., California WHR types 5M, 5D, 
and 6) will also be identified and protected.
    Several protective prescriptions apply in old forest areas, based 
on their location with respect to other management needs. Where 
possible, managers are directed to avoid applying the ``strategically 
placed landscape fuel treatments'' in Old Forest Emphasis Areas. 
However, placement of these strategic fuel treatments may be required 
within Old Forest Emphasis Areas to minimize the risks to human life 
and property, sensitive resources, or protect the Old Forest Emphasis 
Area from loss to wildfire. In Old Forest Emphasis Areas (as in spotted 
owl home range core areas), fuel treatments will be limited to the 
removal of material necessary to reduce surface and ladder fuels 
sufficient to achieve an average flame length of 1.8 m (6 ft) or less 
if the stand were to burn under 90th percentile fire weather 
    When treatments are necessary within Old Forest Emphasis Areas, 
prescribed fire is the first priority to achieve the fuels objectives, 
rather than mechanical treatment. When prescribed fire will not achieve 
fuels objectives, mechanical thinning of understory trees less than 30 
cm (12 in) dbh will be used to achieve the fuels objectives. However, 
in some instances those treatments will not achieve the fuels 
objectives due to existing stand conditions. In those situations 
incidental mechanical thinning of trees up to 51 cm (20 in) dbh and 
canopy reductions of up to 20 percent may be conducted in 28 to 61 cm 
(11 to 24 in) dbh stands with greater than 40 percent canopy cover. An 
additional analysis of suitable owl habitat will be conducted before 
applying the mechanical thinning of up to 51 cm (20 in) dbh and canopy 
reductions of up to 20 percent prescription in Old Forest Emphasis 
Areas. This prescription may only be utilized when sufficient suitable 
owl habitat exists to satisfy the requirements of a home range core 
area within 2.4 km (1.5 mi) of the nest site or activity center. This 
site specific analysis will be documented in the project environmental 
assessment. A minimum of 50 percent canopy cover will be retained on 
the westside and 30 percent will be retained on the eastside following 
any mechanical fuel treatments in Old Forest Emphasis Areas;
    (5) The General Forest designation is that area outside of other 
designations. It consists of about 1.69 million ha (4.17 million ac) 
(after subtraction of overlapping allocations with higher priority). In 
the General Forest lands, spotted owl home range core areas and PACs 
are protected as described in the previous paragraphs. Within General 
Forest that is outside spotted owl PACs and home range core areas, no 
trees greater than 51 cm (20 in) dbh will be removed and canopy cover 
will not be reduced more than 20 percent below current conditions. A 
minimum of 50 percent canopy cover will be retained on the westside and 
30 percent will be retained on the eastside following mechanical 
treatments. The four largest snags per acre over 38 cm (15 in) dbh will 
be retained.
    (6) The threat zone of the urban wildland intermix consists of all 
areas on Forest Service lands that are between 0.4 km (0.25 mi) and 2.4 
km (1.5 mi) of human structures. Recent analysis indicates that this 
area contains over 849,823 ha (2,100,000 ac) or about 18 percent of the 
national forest lands in the Sierra Nevada (K. Barber, USFS, pers. 
comm. 2003). The FEIS stated that about 32 percent of the known 
activity centers occurred within the threat zone (USFS 2001a). The 
threat zone overlaps about half of the California spotted owl PACs (an 
indication of the extensive spread of human development in the region), 
and about 29 percent of the total PAC acres are overlapped by the 
threat zone. Generally, no trees greater than 51 cm (20 in) dbh will be 
removed, and canopy cover will not be reduced more than 20 percent 
below current levels in the threat zone. A minimum of 50 percent canopy 
cover will be retained on the westside and 30 percent will be retained 
on the eastside. The four largest snags per acre over 38 cm (15 in) dbh 
will be retained. Strategically placed landscape treatments will be 
implemented to achieve fuels objectives within the Threat zone. Spotted 
owl PACs will be established and managed as described in (2) above, 
but, in an effort to balance the need for effective fuels reductions 
treatments with conservation of owl habitat, the S&GS did not establish 
home range core areas in the Threat zone. Instead, site-specific 
analysis will determine whether sufficient suitable habitat exists to 
satisfy the requirements of a home range core area within 2.4 km (1.5 
mi) of the nest site or activity center. Where sufficient habitat will 
remain within that area, fuels treatments that remove trees up to 51 cm 
(20 in) dbh and reducing canopy cover by up to 20 percent, but 
resulting in no less than 50 percent canopy cover post-treatment, may 
be utilized outside of PACs in 28 to 61 cm (11 to 24 in) dbh stands 
with greater than 60 percent canopy cover. Otherwise, the treatment 
will be constrained to removal of trees less than 30 cm (12 in) dbh. 
The site-specific analysis will be documented in the project 
environmental assessment.
    (7) The Defense zone of the Urban Wildland Intermix includes those 
areas of national forest land that are within 0.4 km (0.25 mi) of human 
structures. The most recent available estimate indicates that the 
Defense zone totals about 137,995 ha (341,000 ac) of national forest 
lands (K. Barber USFS pers comm. 2003), representing about three 
percent of the national forest lands in the Sierra Nevada. About 4.0 
percent of the California spotted owl activity centers in the Sierra 
Nevada occur within the Defense zone (USFS 2001a). The Defense zone 
overlaps portions of about half of all California spotted owl PACs on 
Sierra national forest lands, but, based on experience in early 
implementation of the SNFPA, the Defense zone includes only about 4 
percent of the total PAC acreage, as a result of its narrow, linear 
form (K. Barber USFS pers comm. 2003). This area is the highest 
priority for fuel treatments, and the relatively intensive treatments 
allowed in this zone may result in stands that are not suitable for 
California spotted owls. In the Defense zone, mechanical treatments 
will be prohibited within a 152 m (500-foot) radius buffer around a 
spotted owl nest site or activity center.
    (8) Vegetation treatments will occur on no more than 30 to 40 
percent of each watershed. These vegetation treatments will result in 
stand conditions meeting the definition of suitable owl habitat.
    Effects of The Quincy Library Group Pilot Project--In 1998, the 
HFQLG designated areas on the Lassen, Plumas, and Tahoe National 
Forests that would be treated for creation of a landscape-based fuels 
reduction program. The Record of Decision for the SNFPA (USFS 2001b) 
directed that all SNFPA S and Gs applying to California spotted owls 
will be implemented in the HFQLG pilot project, resulting in the 
inability to carry out about ten percent of the Defensible Fuel Profile 
Zones that had been proposed in the original HFQLG Environmental Impact 
Statement (USFS 2001b). As stated earlier, the expected harvest volume 
of 138 mmbf per year from the HFQLG area would be less than the amount

[[Page 7600]]

harvested on the three forests during the late 1990s. However, in the 
first two years of implementation, the project has harvested a total of 
about 60 mmbf (M. Carroll-Martin, USFS, pers. comm. 2003), so 
anticipated effects described in the FEIS, which included a decrease in 
owl habitat of 5 to 8 percent (USFS 2001a), may be occurring at a 
slower rate than anticipated.
    Effects of future habitat modification by fuel treatments and 
wildfire--Under the SNFPA, fuel treatments will be applied on a 
relatively small portion of the Sierra Nevada. Prescribed fire 
treatments would be used on less than six percent of the forested area; 
prescriptions thinning trees below 30 cm (12 in) dbh on about three 
percent; thinning of trees 30 to 51 cm (12 to 20 in) dbh on less than 
one percent; and thinning of trees over 51 cm (20 in) dbh on less than 
one half of one percent (derived from data in USFS 2001a and K. Barber, 
USFS, pers comm. 2003) However, because spotted owl habitat is in a 
condition that favors the spread of intense wildfire, many of the 
treatments will be focused on spotted owl habitat.
    According to a database of treatments projected to occur over the 
next 20 years provided to us by the Forest Service (Service 2001), 
SNFPA mechanical treatments will treat approximately 25 percent of 
suitable owl habitat in the Sierras. However, these treatments will not 
be equally distributed among the forests. Mechanical treatments on the 
Lassen, Plumas, and Tahoe National Forests (forests comprising the QLG 
pilot project area) will treat 31, 28, and 31 percent, respectively, of 
spotted owl habitat.
    According to the SNFPA FEIS (USFS 2001a), only a small amount of 
spotted owl habitat is expected to be rendered completely unsuitable by 
fuels treatments and wildfire. The total habitat area projected to be 
lost to both causes in the first decade is about 26,304 ha (65,000 ac) 
and in the second decade, about 23,876 ha (59,000 ac). The projection 
for the second decade is less because the most intense fuels treatments 
will take place in high risk areas in the first decade. In total, this 
loss would represent about three percent of the estimated existing 
habitat over the next twenty years. On a landscape basis, this loss 
will be overcome by a projected overall increase in high quality 
habitat of about 13 percent over the next fifty years (USFS 2001a). 
This increase is expected to occur as today's young and mid-aged stands 
mature into larger size classes, assisted by the thinning and reduction 
in intense wildfire that are among the objectives of the SNFPA. Habitat 
suitability for the primary prey species, the northern flying squirrel 
and dusky-footed woodrat, is also projected to increase (USFS 2001a).
    The primary area where fuel treatments would remove large trees and 
reduce canopy cover to the point of unsuitability for owls would be the 
Defense zone of the wildland/urban interface. The FEIS estimated that 
about four percent of the known spotted owl activity centers fell 
within the Defense zone (USFS 2001a). More recent analysis indicates 
that the Defense zone overlaps some portion of 21 percent of all PACs; 
and Defense zone prescriptions could apply on an average of 35 ha (86 
ac) of those affected PACs. However, only about four percent of the 
overall PAC acreage in the Sierra Nevada occurs within the Defense zone 
(Klaus Barber, USFS, pers. comm. 2003), so this effect should be 
    While the S and Gs provide some protection for a 152 m (500-foot) 
radius (about 7 ha (18 ac)) around known activity centers that are 
found in the Defense zone, canopy cover in the remainder of the Defense 
zone could potentially be reduced to the point that it will probably be 
unsuitable for nesting, roosting, or foraging by spotted owls. The 
portion of those PACs that will actually be changed from suitable to 
unsuitable is unknown; this will depend on the original condition and 
the site-specific treatment. This effect could lead to reduced 
productivity on these sites through reduction of foraging habitat 
(Blakesley in litt. 2002a, Bart 1995a). While the fuel treatment 
prescription for the Defense zone could potentially be applied on over 
137,591 ha (340,000 ac) only about seven percent of the Defense zone 
area overlaps PACs. The Defense zone treatments will also affect 
foraging areas that are associated with other more distant PACs, but 
this effect should be limited to a relatively small proportion of the 
foraging area by the narrow linear nature of the Defense zone.
    During the early decades of SNFPA implementation, less severe 
habitat modification by fuel treatments and wildfire outside the 
Defense zone will be considerably more extensive. This habitat 
modification will probably be the most important factor affecting 
California spotted owl populations in the next few decades, and such, 
needs careful evaluation in this finding.
    In general, treatments that remove habitat features such as large 
trees, snags, logs, and woody debris or that reduce canopy cover may be 
detrimental to California spotted owls, at least until these features 
can be regenerated by continuing growth of forest stands. As described 
in previous sections, large trees, high degrees of canopy closure, and 
large snags and logs are associated with owl nesting, roosting, and 
foraging habitat, and with the habitat of their primary prey in much of 
the Sierra, the northern flying squirrel. Alternately, treatments that 
retain sufficient canopy cover and habitat features to support 
California spotted owls, while at the same time reducing the risk of 
catastrophic fire, may benefit the species (Weatherspoon et al. 1992, 
Larry L. Irwin and Jack Ward Thomas, National Council for Air and 
Stream Improvement, Inc., in litt. 2002).
    The primary aspects of fuel treatments that would potentially 
affect spotted owl habitat are (1) removal of trees larger than 51 cm 
(20 in.) diameter, which may reduce numbers of existing and potential 
nesting trees and large diameter snags and logs, with an accompanying 
reduction of canopy cover; and (2) removal of trees 30 to 51 cm (12 to 
20 in.) in diameter, with resultant reduction in canopy closure, and 
perhaps to a lesser degree, reduction in numbers of existing nest trees 
and recruitment of potential nesting trees and large diameter snags and 
    Throughout the area of the SNFPA, a general S&G precludes the 
removal of any tree over 76 cm (30 in.) dbh. The prescriptions that 
would allow any extensive harvest of trees of over 51 cm (20 in.) dbh 
(except for incidental removal for operability) are confined to the 
Defense zone. In addition, outside the Defense zone, removal of trees 
over 51 cm (20 in.) dbh would be limited to moderate quality habitat 
(i.e., CWHR 4M and 4D) in the threat zone where this zone overlaps Old 
Forest Emphasis areas or where home range core areas exceed a habitat 
quantity standard. Thus, except for possible eventual long-term effects 
on recruitment of large trees that might result from continued 
extensive thinning of small understory trees (Franklin and Fites-
Kaufmann 1996), most effects of the SNFPA on large trees are confined 
to the Defense zone and, with limitations, to other areas outside PACs 
only if their removal is necessary to allow mechanical treatments.
    Therefore, since effects on large trees are limited, most of the 
effects of the SNFPA would be anticipated to result from the harvest of 
trees in the 30 to 51 cm (12 to 20 in.) size class. A small minority of 
spotted owl nests have been found in trees in this size class (USFS 
2001a), but all known nest sites will be protected, so loss of existing 
nest trees is not expected. Trees in this size class also contribute to 
roost sites, but most

[[Page 7601]]

breeding season roost sites would be expected to be contained within 
PACs, where no mechanical treatments will be allowed. Thus, loss of 
these trees in breeding season roost sites would be confined to the 
Defense zone and to effects of prescribed fire in those areas of PACs 
where managers could use fire without important effects.
    As a result of the above protections, the primary effect of removal 
of trees 30 to 51 cm (12 to 20 in.) dbh will be in foraging areas, 
rather than at nest sites. Because the home range core areas receive 
the heaviest foraging use, the effects could be most important there, 
but everywhere outside the Defense zone, except in the threat zone 
outside home range core areas and PACs, trees 30 to 51 cm (12 to 20 
in.) dbh will only be removed when sufficient habitat exists within 2.4 
km (1.5 mi) to meet the core area habitat requirements. Thus, effects 
on spotted owls due to removal of trees 30 to 51 cm (12 to 20 in.) dbh 
are expected to be limited.
    Another important effect of fuel treatments may be reduction in 
canopy closure. In the Defense zone, the canopy closure could be 
reduced to a level below the 40 percent threshold that defines habitat 
suitable for use by spotted owls, although according to the Forest 
Service, this area is often left at about 40 percent to obtain the 
benefits of shade in the fuel break (K. Barber, USFS pers. comm. 2003). 
In the threat zone, canopy cover may be reduced not more than 20 
percent below current levels, and not below 50 percent cover; and in 
home range core areas in that zone, may not be reduced unless 
sufficient habitat exists within 2.4 km (1.5 mi) to meet the core area 
habitat requirements. In General Forest that is outside PACs, home 
range core areas, and patches of high quality habitat (where cover 
could be reduced by no more than 10 percent), canopy may be reduced by 
20 percent, but generally not to lower than 50 percent cover. In 
westside home range core areas, and in Old Forest Emphasis areas, 
canopy cover may be reduced not more than 10 percent from existing 
levels unless habitat standards are met, and not below 50 percent cover 
    As a result of the above measures, opportunities for reduction of 
canopy closure by more than 10 percent outside the Defense zone would 
be limited to areas outside home range core areas unless the habitat 
standards are met. Where the habitat standard is met, the degree of 
reduction would not exceed 20 percent, and would not go below 50 
percent overall unless the stand was already below 50 percent canopy 
closure. Reduction of canopy closure by 20 percent would potentially 
reduce opportunities for nesting in areas where nesting does not 
currently occur, at least for the short term, but these prescriptions 
would not apply in areas designated as PACs or in any home range core 
areas that do not exceed the habitat standard. In all areas except the 
Defense zone, habitat that currently has a degree of canopy closure 
suitable for foraging use would retain that character after treatment.
    Reduction in canopy closure might potentially have important 
effects on survival and reproduction of spotted owls, especially 
related to effects of exposure to weather and modification of forage 
species habitat. Potential effects of weather on adult and juvenile 
survival (Franklin et al. 2000, North et al. 2000) would be largely 
avoided in 121 ha (300-ac) PACs around all known nest sites and 
activity centers, where only prescribed fire is allowed to treat 
surface and ladder fuels, and where effects to overstory canopy would 
be expected to be minimal. Fuel treatments in PACs would occur only in 
5 percent of PACs per year and 10 percent per decade.
    In addition, reduction in canopy closure might have effects on 
occupancy and reproductive success of California spotted owls. North et 
al. (2000) reported on the positive influence of high foliage volume 
around nest sites on owl reproduction. Effects on this attribute would 
not be anticipated from fuel treatments under the S and Gs. Hunsaker et 
al. (2002) reported that California spotted owl reproductive success 
was correlated with degree of canopy cover within several radii around 
nests, and thus, it might be inferred that even relatively small 
reductions in canopy cover by fuel treatments in foraging areas could 
reduce reproductive success. However, prior to publication of Hunsaker 
et al. 2002, during the process of publication of that study, analysis 
of the data by another Forest Service scientist (Lee 2001) found that 
the statistical methodology of Hunsaker et al. (2002) was flawed, and 
thus, the above inference cannot be supported. The analyses of the data 
by both Hunsaker et al. (2002) and Lee (2001) found that canopy cover 
of at least 50 percent was desirable; that level would be maintained by 
the S and Gs in all areas but the Defense zone. Blakesley (2002a) 
reported that amount of habitat above 40 percent canopy cover was 
positively correlated with owl reproduction, but did not evaluate 
differences between increments of canopy cover. Outside the Defense 
zone, treatments would not reduce higher degrees of cover to below the 
40 percent level.
    In many cases, the renewed growth of the crowns of the remaining 
stand after thinning would be expected to fill in the canopy cover 
within one to two decades, so effects of reduction in canopy closure 
due to thinning of understory trees might be temporary. Additionally, 
the extent of such effects would be tempered by the limitation on fuel 
treatments to less than 40 percent of watersheds (outside the Defense 
zone), and by the direction to focus treatments on the upper two-thirds 
of slopes.
    The Service concludes that no available data firmly indicate that 
the removal of trees and the reduction in canopy cover as prescribed by 
the SNFPA S and Gs and described above would have substantial negative 
effects on California spotted owl reproduction and occupancy, except in 
the Defense zone. This does not mean that negative effects would not 
occur. Such effects are possible, and researchers have suggested that 
subtle effects could be important if they occur on a wide scale (Noon 
et al. 1992). Substantial scientific uncertainty remains regarding the 
effects of fuel treatments in PACs and foraging areas. However, in the 
absence of demonstrated effects, and considering that the potential 
negative impacts are also accompanied by the positive effects of fire 
risk reduction and faster development of high quality habitat, we find 
that the timber harvest and fuel treatments proposed under the SNFPA do 
not constitute a significant threat to the California spotted owl at 
this time.
    Fire on nonfederal Lands--The California Department of Forestry and 
Fire Protection (CDF 2002) reported that over 47,347 ha (117,000 ac) of 
nonfederal lands burned in 2002 and that for the most recent 5 year 
period (1998 to 2002) an average of 47,347 (117,000 ac) of nonfederal 
lands burned per year (CDF 2002). However, these statistics are not 
broken down by habitat type and, thus, do not provide an indication of 
losses for forest lands or spotted owl habitat.
    In general, risk of catastrophic fire is probably lower on 
industrial timber lands than on many Federal forest lands, as a result 
of more active management, especially thinning, in recent decades. Risk 
varies on timber lands in other private ownership, according to the 
degree of timber harvest and fuel reduction.

Threats From Urbanization

    Residential development, both through growth of communities and 
construction of dispersed residences,

[[Page 7602]]

poses a threat to California spotted owls by removing and fragmenting 
suitable habitat for the spotted owl and can remove habitat for prey 
species, especially woodrats. Residential developments also introduce 
and increase urban adapted predators (cats, dogs, skunks, racoons, 
ravens, crows) into spotted owl habitat; these predators may kill 
fledgling spotted owls in the nest or on the ground before they are 
capable fliers. Fires within the range of the California spotted owl, 
which could result in the loss of habitat, are more likely to be human 
caused, especially at the urban interface (NIFC 2002).
    Development that is most likely to result in the loss of spotted 
owl habitat is occurring on private land in the lower elevation 
foothill areas of the Sierra Nevada and in southern California (Verner 
et al. 1992a). Statistics for nine of fifteen Sierra Nevada counties 
within the range of the California spotted owl show these counties are 
currently experiencing varying degrees of urban expansion, and have 
projected population growth rates from 0.7 percent in Sierra county to 
6.2 percent in Calaveras county (Sierra Business Council 1997). The 
amount of private versus public lands in the Sierra Nevada and southern 
California portions of the range varies widely by county. The Sierra 
Nevada Ecosystem Project (1996) core analysis area encompassed almost 
8.5 million ha (21 million ac) in the Sierra Nevada, of which 61 
percent is Federal and 38 percent is nonfederal lands. Estimates from 
the Sierra Business Council (1997) indicate that for the nine Sierra 
Nevada counties in the range of the spotted owl they analyzed, an 
average of 46 percent is private land. These studies do not identify 
specific habitat types within ownerships; however, we assume higher 
elevation (greater than 3,000 ft) lands that are predominately in 
Federal ownership are at a lower risk of loss due to urbanization, 
while lower elevation (less than 3,000 ft) lands, in private ownership 
are more likely at risk of habitat loss. Some information is available 
on the ``projected'' amount of land planned for development by county 
as specified in their General Plans, however, these accounts are not 
sufficiently detailed to identify habitat types that are planned for 
development. McBride et al. (1996) looked at the impacts of development 
in specific habitat types in selected areas in five counties in the 
Sierra Nevada. Their results indicated there was a decrease in crown 
cover and tree density and an increase in impervious surface; however, 
no estimates were given for the rate or amounts of habitat lost 
    Direct and indirect loss and degradation of habitat of California 
spotted owls and their prey is expected to continue in mid and lower 
elevation zones of the Sierra Nevada and southern California ranges 
through residential development (Laymon 1988, Verner et al. 1992b), 
harvest of hardwoods for firewood production (Laymon 1988, Verner et 
al. 1992b), human disturbance, and other consequences of development 
because these are among the fastest growing areas in California (Laymon 
1988, McKelvey and Weatherspoon 1992). Suitable habitat scattered among 
houses and housing developments was not found to be occupied by 
California spotted owls in southern California, although areas adjacent 
to these developments contained dense and productive populations of the 
subspecies (Guti[eacute]rrez 1994). As a result, development has the 
potential to further impair effective dispersal among isolated 
populations (Ruth and Standiford 1994). In the San Bernardino 
Mountains, development is likely to first occur at low elevations. 
Urbanization has similar negative implications for Sierra Nevada 
spotted owls that migrate to lower elevations in the winter (Laymon 
1988, Verner et al. 1992b).
    In southern California, the mountain ranges occupied by California 
spotted owls probably act as habitat islands with limited dispersal 
between them. Under natural conditions, if the spotted owl population 
of one island were reduced or eliminated, that population could be 
sustained or reestablished through immigration from another island. As 
a result, a concern is that individual populations of California 
spotted owls, for example, those in southern California, could become 
isolated from other parts of the subspecies' range, for example the 
Sierra Nevada. As urbanization between mountain ranges continues, 
habitats there may be made unsuitable to support dispersing California 
spotted owls, eliminating immigration and potentially leading to 
extirpation of one or more subpopulations (Verner et al. 1992).
    It is evident urbanization and loss of spotted owl habitat is 
occurring, especially in the Sierra Nevada foothills and in southern 
California. This development is occurring within a variety of habitat 
types including agricultural, grassland, as well as woodlands, and 
conifer forest types used by spotted owls. Development is limited in 
some respects by county general planning efforts that guide development 
for a specified planning period. Based on the limited amount of 
information available we cannot conclude the loss of spotted owl 
habitat is significant nor are the threats from urbanization immediate.
    Miscellaneous Habitat Factors. There are several minor or lesser 
known factors that may influence spotted owl survival. Each is 
discussed below.
    Riparian forests are important habitats for California spotted owls 
in southern California (Verner et al. 1992a). Diversion of surface 
waters and pumping of groundwater depletes water from streams upon 
which such habitats depend. Therefore, such development may lead to 
loss of habitat in some areas and therefore extirpation of California 
spotted owls in those areas (Verner et al. 1992a).
    During the late 1800s, heavy grazing of surface fuels by livestock 
may have reduced the influence or extent of wildfires (University of 
California 1996), and subsequent ingrowth of vegetation on denuded 
soils may have contributed to the heavy fuel loading and tendency 
towards catastrophic fire now found in much of the California spotted 
owl's range. Currently, livestock grazing may impact spotted owls by 
removing cover used by prey species, especially brush used by woodrats 
(Verner et al. 1992b).
    Recreation is the fastest growing use of the national forests (USFS 
2001a). The construction of facilities used for recreation, including 
campgrounds, trails (foot, horse, and off highway vehicle), roads, ski 
resorts, and cabins has likely contributed to the destruction and 
fragmentation of California spotted owl habitat. In addition to habitat 
loss, recreational activities have the potential to disturb spotted 
owls and thereby adversely affect their survival and reproduction 
(Service 2001). The effect of recreation on owls is poorly understood 
and may be an increasing threat to California spotted owls, especially 
in southern California (Noon and McKelvey 1992).
    Sudden oak death is a tree disease caused by the pathogen 
Phytophthora ramorum. It infects a variety of trees, including true 
oaks (Quercus spp.), California bay laurel, tanoak, and madrone (CDF 
2002). Some trees are killed by the disease, while others survive but 
serve as hosts. The disease can be found in 11 coastal counties outside 
the range of the California spotted owl and only one within the range 
(Monterey) (CDF 2002, UC Berkeley, in litt. 2002, Endicott 2002). The 
extent to which the disease may spread and the number of tree species 
it may affect remain undetermined. California spotted owls are forest

[[Page 7603]]

species, thus, tree deaths caused by this pathogen may pose a threat to 
owls or their prey species.
    In summary, threats affecting the California spotted owl's habitat 
by themselves, or in combination with other factors, do not seem to 
pose now or in the foreseeable future a significant threat to the 
continued existence of the California spotted owl such that it warrants 

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

    We found no evidence that overutilization for commercial, 
recreation, scientific, or educational purposes is a threat to the 
California spotted owl. Research by Federal and State agencies, and 
various public institutions and private groups is conducted on the 
California spotted owl, but such research is not known to have a 
negative effect on the species. We are aware that northern spotted owl 
sites are visited by ecotourists (Sacramento Bee, October 27, 2002) and 
photographers, but we are not aware of such visits to California 
spotted owls. Therefore, we believe that overutilization for 
commercial, recreation, scientific, or educational purposes does not 
pose a threat to the continued existence of the California spotted owl.

C. Disease or Predation

    Little is known regarding disease in California spotted owls 
(Verner et al. 1992b, Guti[eacute]rrez et al. 1995). They have a high 
infection rate by blood parasites, with 76 individuals examined showing 
100 percent infection with one or more of Haemoproteus noctuae, H. 
syrnii, Leucocytozoon ziemanni, Trypanosoma avium, microfilariae, and/
or Atoxoplasma spp (Verner et al. 1992b, Gutirrez et al. 1995). 
However, survival rates are high even where blood parasite infection 
rates are high (Verner et al. 1992b, Gutirrez et al. 1995). Infection 
by parasitic worms has been documented in northern spotted owls, 
including round worms, flat worms, and spiny-headed worms (Verner et 
al. 1992b, Gutirrez et al. 1995); and similar infections are likely in 
the California subspecies. External parasites have also been recorded 
in California spotted owls, including louse flies (Icosta americana) 
and chewing lice (Strigiphilus spp).
    In 1999, a strain of the West Nile Virus (WNV) that has a high 
fatality rate in some birds was discovered in the eastern United States 
and more recently has infected humans in California (Russell 2002 and 
CDC 2002). WNV has been detected in dead birds of at least 138 species, 
although cause of death was not conclusively attributed to WNV (CDC 
2002). Although birds, particularly crows and jays, infected with WNV 
can die or become ill, most infected birds do survive (CDC 2002). WNV 
is amplified during periods of adult mosquito blood-feeding by 
continuous transmission between mosquito vectors and bird reservoir 
hosts. Infectious mosquitoes carry virus particles in their salivary 
glands and infect susceptible bird species during blood-meal feeding. 
Bird reservoirs can sustain an infectious viremia (virus circulating in 
the bloodstream) for one to four days after exposure, after which these 
hosts develop life-long immunity. A sufficient number of vectors must 
feed on an infectious host to ensure that some survive long enough to 
feed again on a susceptible reservoir host.
    In 2002, WNV activity has spread to most eastern and mid-western 
states, with 113 cases and 5 human deaths as of August 8, 2002 (United 
States Geological Service (USGS) 2002). We are not aware of any 
infection of spotted owls by the virus, but WNV has been found to 
infect the closely related barred owl (USGS, in litt. 2002), and may 
pose a threat to spotted owls.
    Natural predators are discussed under Natural Mortality in the Life 
History section, above. Natural predation probably has little effect on 
healthy populations. However, as populations become smaller and more 
fragmented, the impacts of natural predation may also become 
significant. Also, the invasion of a new competitor and possible 
predator, the barred owl, is discussed in Factor E.
    In summary, disease or predation factors by themselves, or in 
combination with other factors, do not seem to pose now or in the 
foreseeable future a significant threat to the continued existence of 
the California spotted owl such that it warrants listing.

D. The Inadequacy of Existing Regulatory Mechanisms

    Existing regulatory mechanisms that could provide some protection 
for the California spotted owl include: (1) Federal laws and 
regulations including the Migratory Bird Treaty Act (16 U.S.C. 703-
712), the Multiple-Use Sustained-Yield Act of 1960 (16 U.S.C. 528-531), 
the Wilderness Act of 1964 (16 U.S.C. 1131-1136), the National 
Environmental Policy Act (42 U.S.C. 4321 et seq.), the Forest and 
Rangeland Renewable Resources Planning Act of 1974 (16 U.S.C 1601-1614, 
Sec. Sec.  1641-1647), and the Sierra Nevada Forest Plan Amendment 
(USFS 2001a and b); and (2) State laws including the California 
Environmental Quality Act (CEQA) (Pub. Resources Code Sec.  21000 et 
seq.), the California Forest Practice Rules (14 C.C.R. Sec.  895 et 
seq.), and the California Fish and Game Code Sec. Sec.  1 et seq. Local 
land use processes and ordinances are subject to CEQA.
    The Migratory Bird Treaty Act (MBTA) prohibits ``take'' of any 
migratory bird. ``Take'' is defined as to pursue, hunt, shoot, wound, 
kill, trap, capture, or collect, or attempt to pursue, hunt, shoot, 
wound, kill, trap, capture, or collect . However, no provisions in the 
MBTA prevent habitat destruction except that causing direct mortality 
or destruction of active nests.
    The Wilderness Act of 1964 established a National Wilderness 
Preservation System made up of federally owned areas designated by 
Congress as ``wilderness areas'' for the purpose of preserving and 
protecting designated areas in their natural condition. Commercial 
enterprise, road construction, use of motorized vehicles or other 
equipment, and structural developments are usually prohibited within 
designated wilderness areas. The Wilderness Act has protected some 
California spotted owl habitat from development or other types of 
habitat conversions; however, it does not have any provisions specific 
to the protection of the species.
    The National Environmental Policy Act of 1969, as amended (NEPA), 
requires all Federal agencies to formally document and publicly 
disclose the environmental impacts of their actions and management 
decisions. NEPA documentation is provided in either an environmental 
impact statement, an environmental assessment, or a categorical 
exemption, and may be subject to administrative or judicial appeal. The 
Forest Service considers the California spotted owl a species of 
concern. Therefore, part of the analysis generated by the Forest 
Service to direct management decisions under NEPA may include a 
biological evaluation that discloses potential impacts to species of 
concern on a project by project basis.
    The Multiple-Use Sustained-Yield Act of 1960, as amended, (MUSY) 
provides direction that the national forests be managed using 
principles of multiple use and to produce a sustained yield of products 
and services. Specifically, MUSY provides policy that the national 
forests are established and shall be administered for outdoor 
recreation, range, timber, watershed, and wildlife and fish purposes. 
Land management for multiple uses has inherent conflicts.

[[Page 7604]]

However MUSY directs resource management not to impair the productivity 
of the land while giving consideration to the relative values of the 
various resources, though not necessarily in terms of the greatest 
financial return or unit output. MUSY provides direction to the Forest 
Service that wildlife, including the California spotted owl, is a value 
that must be managed for, though discretion is given to each forest 
when considering the value of this species relative to the other uses 
for which it is managing. Although MUSY could provide some protection 
for the owl, it does not have any provisions specific to the 
conservation of the owl or its habitat.
    The Forest Service also manages national forests under the Forest 
and Rangeland Renewable Resources Planning Act of 1974 (RPA) as amended 
by the National Forest Management Act of 1976 (NFMA). Implementing 
regulations for NFMA (36 CFR 219.20(b)(i)) require all units of the 
National Forest System to have a land and resource management plan 
(LRMP). The purpose of the LRMP is to guide and set standards for all 
natural resource management activities over time. NFMA requires the 
Forest Service to incorporate standards and guidelines into LRMPs, 
including provisions to support and manage plant and animal communities 
for diversity, and the long-term range-wide viability of native and 
desired non-native species. Standards and guidelines are based on the 
suitability and capability of the specific land area in order to meet 
overall multiple-use objectives.
    Beginning in 1991 and culminating with the signing of the Record of 
Decision for the Sierra Nevada Forest Plan Amendments in 2001, the 
Forest Service initiated several Sierra Nevada-wide planning efforts to 
maintain viability of California spotted owls on national forest land. 
These efforts gathered and analyzed technical information as well as 
developed and refined management direction. These efforts included a 
technical assessment of the current status of the California spotted 
owl and issuance of interim guidelines (Verner et al. 1992a) for 
protecting California spotted owl habitat in January of 1993. The 
guidelines were adopted as the 1993 California Spotted Owl Sierran 
Province Interim Guidelines Environmental Assessment and incorporated 
as amendments into the Forest Service's Land and Resource Management 
    These guidelines were intended to maintain management options and 
short-term population viability for the California spotted owl in the 
short term (maximum of five years; Verner 1999) until a conservation 
strategy for the owl was developed. The primary objectives of the 
interim guidelines were to protect known nest stands, protect large old 
trees in timber strata which provide suitable owl habitat, and reduce 
the threat of stand-destroying fires. However, they allowed degradation 
of suitable nesting and roosting habitat by allowing timber harvest 
(except in protected activity centers and some acreage in spotted owl 
habitat areas) to reduce canopy cover to 40 percent in timber types 
selected by owls and below 40 percent in other types used by owls 
according to their availability on the landscape. The estimated time of 
recovery of these treatments was five years. Under the interim 
guidelines, no mechanism existed to evaluate cumulative impacts of 
timber harvest on California spotted owls in national forests. After 
1993 when baseline surveys for the species were completed within Forest 
Service managed lands, forest management continued without further 
requirements to survey for the owl.
    In 1995 the Forest Service released a draft environmental impact 
statement (EIS) for a long-term management plan for California spotted 
owl habitat. Final direction was not issued due to new scientific 
information provided by the Sierra Nevada Ecosystem Project (SNEP) 
report released in 1996. In 1998 the Forest Service initiated a 
collaborative effort to incorporate new information from the SNEP 
report into management of Sierra Nevada national forests. This effort 
became known as the Sierra Nevada Framework for Conservation and 
Collaboration (Framework).
    As part of the Framework, the Forest Service developed the SNFPA 
Environmental Impact Statement, for which a record of decision was 
issued on January 12, 2001 (USFS 2001b). This effort amended the land 
and resource management plans of Forest Service administered lands 
addressed by the Framework. The SNFPA addresses five problem areas: old 
forest ecosystems and associated species; aquatic, riparian, and meadow 
ecosystems and associated species; fire and fuels; noxious weeds; and 
lower westside hardwood ecosystems. The SNFPA included a conservation 
strategy for California spotted owls, which replaced the interim 
    Subsequent to the establishment of management direction by the 
Record of Decision of the SNFPA, Region 5 of the Forest Service has 
undertaken two efforts that may result in changes in the anticipated 
impacts of the SNFPA. The first is a management review of the SNFPA 
(USFS 2002b), and the second is planning for implementation of an 
Administrative Study on the Lassen and Plumas National Forests that 
would evaluate the effects of extensive fuels treatments on the 
California spotted owl (67 FR 72136). As of yet, neither of these 
efforts have formally established management direction, so their 
potential effects are uncertain and subject to change before 
implementation. Therefore, their potential effects are not included in 
the assessment of threats to the California spotted owl under this 12-
month finding. However, because the outcome of each of these efforts 
could substantially affect California spotted owls, we will monitor the 
development of management direction, offer scientific assistance, and 
review the effects at a later date, if necessary.
    The SNFPA applies only to national forests in the Sierra Nevada and 
Modoc Plateau. Spotted owls in southern California are protected by 
measures developed by each forest (Ruth and Standiford 1994), which are 
currently revising their LRMPs to include a strategy to manage habitat 
for the owl. As a result, no comprehensive strategy currently exists 
for the California spotted owl on national forests in southern 
California. The four Forests have completed an ecological assessment 
(Stephenson and Calcarone 1999) and in September 2001 published a 
Notice of Intent (NOI) to prepare a single Environmental Impact 
Statement and Record of Decision (USFS 2001c). The draft EIS is 
scheduled for release in 2003. Included in the Purpose and Need 
statement of the NOI is the intent ``To more adequately protect plant 
and animal species and their habitat.'' The Proposed Action also 
recognizes that one of the most compelling needs for change in Forest 
Plan direction is maintenance of viable populations of plant and animal 
    Other Federal agencies have general or specific policies and 
regulations that would apply to the owl. The National Park Service 
protects all species from collection, with exemptions only for 
scientific testing (36 CFR 2.5). The BLM has listed the owl as a 
Special Status Species that should be addressed prior to approval of 
actions that may impact the species on BLM lands (USDI 2001).
    State. Section 3503.5 of the California Fish and Game Code (CDFG 
2002) provides that it is unlawful to take, possess, or destroy any 
birds in the order Strigiformes (owls) or to take, possess, or destroy 
their nests or eggs. This restriction applies only to individual owls, 
their nests and eggs and does not place restrictions on

[[Page 7605]]

inactive nests or habitats used by spotted owls.
    The CDFG has identified the California spotted owl as a Species of 
Special Concern (CDFG 1978). This status applies to animals not listed 
under the Federal or the California Endangered Species Act but which 
appear to be vulnerable to extinction. The intent of this designation 
is to obtain special consideration for these species in the project 
planning process and to focus attention on the species to avert the 
need for listing under either State or Federal laws. CEQA requires that 
impacts to such species be mitigated. Although state and local agencies 
have discretion to approve projects that impact a Species of Special 
Concern, such impacts must be mitigated.
    In 1970 the State of California enacted the CEQA (CEQA 1996a). CEQA 
requires a full disclosure of the potential environmental impacts of 
public or private projects carried out or authorized by nonfederal 
agencies within the state of California. The stated goals are to, 
``identify the significant environmental effects of their actions; and, 
either avoid those significant environmental effects, where feasible; 
or mitigate those significant environmental effects, where feasible.'' 
The CEQA Guidelines provide criteria to the State or local public 
agency with permitting authority or jurisdiction over a project (lead 
agency) in determining whether a project may have significant effects 
(CEQA 2001b). Section 15065 of the CEQA Guidelines, as amended, 
requires a finding of significance if ``[t]he project has the potential 
to substantially degrade the quality of the environment, substantially 
reduce the habitat of a fish and wildlife species, cause a fish or 
wildlife population to drop below self-sustaining levels, threaten to 
eliminate a plant or animal community, reduce the number or restrict 
the range of an endangered, rare or threatened species' (CEQA 2001b).
    CEQA requires review of any project that is undertaken, funded, or 
permitted by a State or local governmental agency. If a project with 
potential impacts on the California spotted owl were reviewed, CDFG 
personnel could determine that, although not listed, the spotted owl is 
a de facto endangered, threatened, or rare species under section 15380 
of CEQA. Once significant effects are identified, the lead agency has 
the option of requring mitigation for effects through changes in the 
project or to decide that overriding considerations make mitigation 
infeasible (Sec.  21002) (CEQA 1996a), athough such an override 
requires justification and is rarely implemented.
    The lead ageny is responsible for conducting a review of the 
project and consulting with the other agencies concerned with the 
resources affected by the project. If significant effects are 
identified by the lead agency, an Environmental Report (EIR) must be 
prepared that analyzes the effects of the action, proposed mitigation, 
and explains why any potential mitigation measure is not feasible. 
After review of the EIR by the public and relevant agencies, the lead 
agency has the option of disapproving the project, requiring mitigation 
for effects through changes in the project, or to decide that 
overriding considerations make mitigation infeasible and allow the 
project to go forward.
    If a project with potential impacts on the California spotted owl 
were reviewed, CDFG personnel could determine that, although not 
listed, the spotted owl is a de facto endangered, threatened, or rare 
species under section 15380 of CEQA. Once significant effects are 
identified, the lead agency has the option of requiring mitigation for 
effects through changes in the project or to decide that overriding 
considerations make mitigation infeasible (Sec.  21002)(CEQA 1996a). 
CEQA analysis and subsequent requirements for mitigation (e.g., legacy 
hardwoods) would result in protection of spotted owl habitat 
components. However, CEQA does not compel a comprehensive strategy for 
protection of this species.
    Under provisions of CEQA, an independent regulatory program can be 
certified by the Secretary of the Resources Agency, and allow 
submission of a plan in place of an EIR. In 1973 the State of 
California enacted the Z'berg-Nejedly Forest Practice Act of 1973 (CDF 
2000), to ensure that timber harvest was done in a manner that would 
preserve fish, wildlife, forests, streams and other water sources. 
Additional rules, called Forest Practice Rules (FPR) (CDF 2002), were 
promulgated by the State Board of Forestry and Fire Protection and are 
administered by the California Department of Forestry and Fire 
Protection (CDF) to carry out the intent of the Forest Practice Act. 
CDF ensures that private landowners abide by the FPRs when harvesting 
trees. Although there are specific exemptions in some cases, compliance 
with the Forest Practice Act and Board rules apply to commercial 
harvesting operations for landowners of all sizes. The FPRs require 
landowners prepare and submit for approval by CDF, a Timber Harvesting 
Plan (THP). A THP is the blueprint outlining what timber will be 
harvested, how it will be harvested, and the steps that will be taken 
to prevent damage to the environment. A THP functions as the equivalent 
of an EIR under CEQA.
    THPs are prepared by Registered Professional Foresters (RPF) who 
are licensed to prepare detailed plans pursuant to California's 
Professional Foresters Law (PFL) of 1972 (CDF 2002). A RPF is defined 
as ``..a person who, by reason of his or her knowledge of the natural 
sciences, mathematics, and the principles of forestry, acquired by 
forestry education and experience, performs services, including, but 
not limited to, consultation, investigation, evaluation, planning or 
responsible supervision of forestry activities when [such] professional 
services require the application of forestry principles and 
techniques''. A person must have seven years experience in forestry 
work and may substitute a Master of Forestry or Bachelor of Science of 
Forestry degree in lieu of four years of forestry work experience and 
must pass a comprehensive examination administered by the Professional 
Foresters Examining Committee.
    The FPRs provide that a THP must contain information on the 
presence and protection of known habitat or individuals of any listed 
species and information on the presence and protection of non-listed 
species that may be impacted by the timber operation. If information 
provided in a proposed THP is incorrect, incomplete or misleading in a 
material way, or is insufficient to evaluate significant environmental 
effects, the FPRs require disapproval of the THP. Under the FPRs, a 
species can be classified as a ``sensitive species'' if it is found 
that the California population requires timberland as habitat for 
foraging, breeding, or shelter, the California population is in decline 
or there is a threat from timber operations, and continued timber 
operations under the current rules of the Board will result in a loss 
of the California population viability. The California spotted owl is 
not currently listed as a sensitive species. The FPRs require a 
cumulative effects assessment to address any significant known wildlife 
or fisheries concerns where there is a substantial reduction in 
required habitat or the project will result in significant interference 
with the movement of resident or migratory species. The CDF requires 
measures including, but not limited to, a buffer that protects the 
nest, screening, perch, and replacement trees if a spotted owl nest is 

[[Page 7606]]

during the planning or operations phase of a THP (Cunningham, CDF, 
pers. comm. 2002).
    The implementation of the FPRs can take several forms from 
development of smaller individual site specific THPs to the so called 
Option B--landscape scale Sustained Yield Plans (SYPs). Currently there 
are two approved SYPs that cover approximately 73,700 ha (182,000 ac) 
of California spotted owl habitat north of Lake Almanor. This is 
approximately 8 percent of the estimated acres of potential suitable 
habitat on private timberlands (Verner et al. 1992a).
    Another way to comply with the FPRs is development of the so called 
Option A-Maximum Sustainable Production (MSP) plan which provides a 
broad set of criteria that guides the individual THP process for the 
ownership (FPRs Sec. Sec.  913.11, 933.11, 953.11)(CDF 2002). The 
primary goal of the MSP is to document and provide for the long term 
sustained yield of timber products.
    Sierra Pacific Industries (SPI) is the largest private commercial 
timberland owner within the range of the California spotted owl. SPI 
owns approximately 376,351 ha (930,000 ac) of timberland within the 
range of the spotted owl. All of SPI's commercial timberland is 
harvested under two CDF approved MSPs (one for the north and one for 
the south) (SPI 1999 a & b). SPI continuously collects and maintains an 
inventory of vegetation/habitat over the entire ownership. The 
ownership is inventoried in 1.6 ha (4 ac) plots with detailed 
information on tree species, overstory, understory, size class, snag 
class, etc. Thus, SPI continuously maintains information on over 
350,000 plots with 10 percent of the land ownership inventoried each 
year and all plots are inventoried each decade. Information is also 
collected on wildlife including location of California spotted owl nest 
sites. SPI uses the baseline inventory to model growth and yield of 
timber stands. This sophisticated modeling projects forest conditions 
for a 100 year planning horizon with a mix of silvicultural and 
cultural practices. SPI models project an increase of large tree/closed 
canopy conditions from about 20 percent of the landscape in year one 
(current condition) to 65 percent in year 80 and stabilizing to 55 
percent in year 100. The average diameter of trees increases from 18 in 
class (current condition) to 32 in class and projections anticipate 
maintenance of the higher proportion of larger tree class over time 
with harvest practices.
    The implementation of the FPRs focus primarily on sustainable 
timber harvest with a secondary focus on fish and wildlife. With no 
requirements to implement strategies to specifically manage and protect 
habitats that spotted owls use, some habitat elements may not be 
protected adequately. For example the FPRs do not require retention of 
structural elements such as downed woody debris that provide habitat 
for spotted owl prey species. However, the FPRs provide that all snags 
within the logging area be retained to provide wildlife habitat. There 
are exceptions, such as allowing harvest of merchantable snags in any 
location, snags whose felling is required for insect or disease control 
or safety reasons, and snags proposed for harvest by an RPF, where 
there is justification that there will not be a significant impact to 
wildlife. These exceptions provide discretion to timber operators on 
the ground to remove snags without specific review of the potential 
effects on owl habitat, unless addressed through late successional 
forest stands regulation. If a nest site is only discovered and 
buffered during harvest operations, impacts that have already occurred 
to the foraging and roosting habitat surrounding the nest site may not 
be adequately addressed. Furthermore, if planning or harvest operations 
occur outside the nesting season, nests may not be detected at all, and 
those habitats will receive no protection. Certain timber operations 
can be exempt from the THP process, including the harvest of dead and 
dying trees in amounts less than 10 percent of the volume of timber per 
    The FPRs provide that in preparing a THP, the RPF may conduct the 
cumulative impacts assessment based on information that is reasonably 
available before submission of the THP. The effects of timber harvest 
in a watershed could be determined, cumulatively, to result in impacts 
not assessed on a site by site basis. CDF with support from CDFG for 
fish and wildlife species, determines the sufficiency of the assessment 
based on information in its files or on comments received during the 
notice and comment period. However, less than 25 percent of THPs are 
field checked by the CDFG, and most THPs do not adequately assess 
cumulative impacts (Berbach pers. comm. 2002). This level of review 
accounts for approximately 50 to 60 percent of the acres in THPs 
submitted, where the focus is often exclusively on listed species due 
to budget, priorities, and staffing issues (Garrison, CDFG, pers. comm. 
2002). In smaller, non-industrial THPs, a complete cumulative effects 
analysis of past, present, and reasonably foreseeable actions at the 
watershed scale is not always provided by the land owner or the RPF 
preparing a THP. This is due to factors such as lack of funding to 
perform adequate watershed level analysis, lack of information about 
other private parcels in the watershed, and sometimes lack of knowledge 
of available resources, including studies conducted on larger public 
and private ownerships that would provide such information (Cunningham, 
CDF, pers. comm. 2002).
    Approximately 80 percent of habitat for the California spotted owl 
on private lands is in the ownership of SPI timberlands and accounts 
for approximately 10-12 percent of the range of the spotted owl. All of 
SPI properties operate under a State required long term plan for timber 
production and resources management. As part of the requirement by the 
State, SPI's MSP does provide a sophisticated projection for long term 
increases in habitats characterized as suitable for nesting, roosting, 
foraging and dispersal by spotted owls. These habitats are projected to 
be well distributed across the landscape. SPI has taken steps to 
collect and analyze information on spotted owl nest locations, breeding 
success, and habitat use to support their conclusion that long term 
projections include an increase in habitat for spotted owls.
    The timber management plans in place on private lands are not 
developed or implemented with the purpose of protecting habitat for 
California spotted owls. However, it appears that the State FPRs and 
the plans in place over a significant portion of the range of the 
spotted owl on private lands would result in some benefits to spotted 
owls. These plans would benefit from further evaluation and peer review 
to verify their contribution to spotted owl viability in the Sierra 
    Therefore, we believe there is no substantive information that 
indicates there are significant or immediate threats to California 
spotted owl viability because of the lack of regulatory mechanisms.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

    Climate and Climate Change. Climate may influence vital rates 
(survival, fecundity, and recruitment) of spotted owls directly, or 
through indirect means such as effect on prey populations (LaHaye et 
al. 1994, Verner 1999, Franklin et al. 2000, North et al. 2000). In 
southern California, drought was postulated to affect spotted owl 
population dynamics through its effects on prey (LaHaye et al. 1994), 
and statistical modeling showed that drought is associated with reduced

[[Page 7607]]

fecundity (LaHaye et al., in litt. 2002). North et al. (2000) found 
synchronous low reproductive success of owls in the Sierra National 
Forest and Sequoia and Kings Canyon National Parks correlated to high 
spring precipitation (as was found for northern spotted owls by 
Franklin et al. (2000)) and lower spring temperatures, presumably due 
to effects of weather on prey species. Statistical modeling indicated 
lower fecundity in years with higher spring precipitation in spotted 
owls in southern California (LaHaye et al., in litt. 2002). Results of 
a modeling study conducted by Franklin et al. (2000) suggested that 
northern spotted owl populations may experience periods of decline 
solely due to climatic variation; i.e., even if habitat conditions 
remain unchanged, northern spotted owl populations may decline. The 
synchronous declines in reproduction observed by North et al. (2000) 
are of concern because as populations decline, the effects of 
catastrophes, especially those having a synchronous effect on 
populations, will have an increasing importance in determining rates of 
population change (Peery 1999, Franklin et al. 2000).
    Climate may have greater impacts on spotted owls when working in 
concert with habitat degradation. Studies by Franklin et al. (2000) for 
northern spotted owls and by North et al. (2000) for California spotted 
owls indicate the important role habitat may play in buffering against 
the negative effects of climate. Franklin et al. (2000) found that the 
best model to predict adult survival included interactions between 
climate and habitat. Habitat quality, as defined by an optimal mix of 
edge and interior habitat, appeared to buffer the effects of climatic 
variation on survival, presumably because such habitats provided 
sufficient prey resources. North et al. (2002) found that the 
characteristics of nest site structures can modify microclimate 
conditions. Despite synchronous low reproduction, certain nests 
consistently exhibited higher reproductive success. In oak woodlands, 
these nests were on shrubby, north-aspect slopes in trees or snags 
surrounded by a well-developed canopy and in conifer forests they were 
overtopped by a canopy with a high foliage volume. The authors 
concluded that reproduction is influenced by both regional weather 
conditions and nest-site canopy structure, which protects fledglings 
from detrimental weather. Thus, if habitat features that buffer the 
effects of weather are removed, climate may have greater negative 
effects on spotted owls.
    The last century has included some of the most variable climate 
reversals, at both the annual (extremes and high frequency of El 
Ni[ntilde]o and La Nina events) and near decadal scales (periods of 
five to eight year drought and wet periods) documented (USFS 2001b). 
These events may have negative effects on California spotted owls. 
Modeling of population response to climate in northern spotted owls by 
Franklin et al. (2000), suggests that cold high precipitation springs, 
as would be expected in California during El Nino years, lead to higher 
mortality. Alternately, low precipitation (as expected during La Nina 
years) may have negative effects on prey populations (Verner et al. 
    Changes in climate that occur faster than the ability of endangered 
species to adapt could cause local extinctions (United States 
Environmental Protection Agency (USEPA) 1989). Analysis of the 
Antarctic Vostok ice core has shown that over the past 160,000 years, 
temperatures have varied with the concentrations of greenhouse gasses 
such as carbon dioxide and methane (Harte 1996). Since the pre-
industrial era, atmospheric concentrations of carbon dioxide have 
increased nearly 30 percent, methane concentrations have more than 
doubled, and nitrous oxide (another greenhouse gas) levels have risen 
approximately 15 percent (USEPA 1997). The burning of fossil fuels is 
the primary source of these increases (USEPA 1997). Global mean surface 
temperatures have increased 0.3-0.7 Celsius (0.6-1.2 Fahrenheit) since 
the late 19th century (USEPA 1997).
    Climate modeling indicates that the overall effects of global 
warming on California will include higher average temperatures in all 
seasons, higher total annual precipitation, and decreased spring and 
summer runoff due to decreases in snowpacks (USEPA 1989, USEPA 1997). 
California spotted owls are susceptible to heat stress (Weathers et al. 
2001) and are therefore likely to suffer from increased temperatures. 
Higher precipitation during the breeding season may increase mortality 
of spotted owls (Franklin et al. 2000). Decreased runoff from snowpacks 
may cause decreases in the extent or quality of riparian habitats, 
which are important for California spotted owls, especially in southern 
California (Verner et al. 1992a).
    Southern California forests in San Bernardino, Riverside, and San 
Diego counties are experiencing the worst drought in more than 450 
years (Loe in litt. 2002). Thus, the spotted owl population in these 
habitats may be at significant risk. Conifers stressed by drought, 
combined with overstocked conditions, pollution, mistletoe, root 
disease, and insect infestations are experiencing mortalities of up to 
40 percent in some areas (Loe in litt. 2002). As larger older trees 
along with canopy layers are lost due to mortality, the effects to 
spotted owl prey and nesting habitat will likely continue for 
significant periods. As stated above, the San Jacinto Mountains are 
experiencing especially high mortality. It is anticipated that most of 
the nesting and roosting habitat in the San Jacinto Mountains will be 
lost. This area supports about 10 pairs of spotted owls, all of which 
could be lost (M. Gertsch, USFS, pers. comm. 2002). Response plans by 
the Forest Service and CDF include removal of dead and infected trees 
to reduce spread of disease, harmful insects, and fire; however, these 
agencies indicated the extent of the impacts far exceed their capacity 
to respond in the short term (Loe in litt. 2002). Planning efforts to 
address the drought mortality by the agencies are underway. As 
previously stated the population of spotted owls in southern California 
are geographically isolated from spotted owls in the north (Sierra 
Nevada range) and may warrant special management consideration.
    Air Pollution. Nitrogen oxides and volatile organic compounds are 
emitted from industrial and automotive sources and transported by wind 
to California spotted owl habitat (USFS 2001a). These compounds react 
under sunlight to release ozone. Snow core samples from the Sierra 
Nevada contain a variety of other contaminants from industrial and 
automotive sources including; hydrogen ions (indicative of acidic 
precipitation), nitrogen and sulfur compounds (NH4, 
SO2, and SO4), and heavy metals (Pb, Fe, Mn, Cu, 
and Cd) (Laird et al. 1986). These pollutants may directly harm 
California spotted owls. In addition to likely direct effects, 
pollutants can negatively affect California spotted owl habitat. Air 
pollution causes damage to trees, which may cause abnormalities and 
retard growth (USFS 2001a). Air pollution also contributes to tree 
deaths, especially by making them vulnerable to attack by insects (USFS 
2001a). Damage and death of trees may reduce forest characteristics 
selected by California spotted owls, such as canopy cover, basal area, 
number of large trees, etc. Tree death also contributes to heavy fuel 
loading and the risk of severe fires (University of California 1996).
    Human Induced Stress and Mortality. Spotted owls have died in 
collisions with vehicles (Verner et al. 1992b). They may also suffer 
from stress caused by human activities and habitat alteration. Wasser 
et al. (1997) measured levels of stress induced glucocorticoid

[[Page 7608]]

hormones in field collected northern spotted owl feces, and found those 
levels to be significantly higher in males having territories centered 
within 0.41 km (0.25 mi) of roads or areas of recent timber harvest. 
Guti[eacute]rrez and Tempel (in litt. 2002) collected similar data on 
California spotted owls. They found significant variation between 
samples, but that variation was not significantly correlated with 
habitat condition, road proximity, or exposure to noise from chainsaws.
    Barred Owl Invasion. Historically, the barred owl was native to 
eastern north America and absent from the range of the California 
spotted owl. Barred owls have expanded their range into western North 
America, moving into the range of the California spotted owl from the 
north. Barred owl populations in California are increasing, especially 
in northwestern California, and the species has now been detected as 
far south as Nevada County, California, in the Sierra Nevada (Dark et 
al. 1998).
    Barred owls have been documented to displace spotted owls from 
their territories and to hybridize with spotted owls (Dark et al. 
1998). There is also circumstantial evidence that barred owls will prey 
on spotted owls (Leskiw and Guti[eacute]rrez 1998).
    The barred owl invasion of western North America has probably been 
facilitated by alteration of habitats by humans. The barred owl is a 
forest species, but does not rely on late successional forests as 
spotted owls do. The establishment of riparian forests and the planting 
of trees that occurred simultaneously with human settlement of the 
northern great plains may have created habitat used by dispersing 
barred owls as they moved west across the midwestern United States and 
southern Canada. Barred owls readily use disturbed habitats, and 
logging in the Rocky Mountains, Cascades, and Sierra Nevada has 
probably facilitated their colonization of forests there.
    In 2002, researchers on the Lassen Study Area found three pairs 
with combinations of spotted owls and ``sparred owls'' (spotted owl/
barred owl hybrids), and one pair of barred owls. None of these birds 
reproduced. No other barred owls or sparred owl combinations were 
reported from the Sierra Study Area or the Sequoia Study Area. Other 
reports had not yet been received as of late October 2002 (Stine 2002).
    The existing population of barred owls in the Sierra Nevada remains 
at a level below one percent that of spotted owls. Although barred owls 
may pose a substantial threat to California spotted owls at some point 
in the future, by themselves, or in combination with other factors, 
they do not nor do other factors seem to pose now or in the foreseeable 
future a significant threat to the continued existence of the 
California spotted owl such that it warrants listing.


    We have carefully assessed the best scientific and commercial 
information available regarding the past, present, and future threats 
faced by this species. We reviewed the petition, information available 
in our files, other published and unpublished information submitted to 
us during the public comment period following our 90-day petition 
finding, and consulted with recognized California spotted owl experts 
and other Federal and State resource agencies. On the basis of the best 
scientific and commercial information available, we find that listing 
the California spotted owl is not warranted at this time.
    In making this finding, we recognize that there are indications 
that the California spotted owl may be experiencing an uncertain levels 
of decline in parts of its range based on demographic studies, and that 
the species may face threats from catastrophic fire and habitat 
modification related to reduction of the risk of catastrophic fire. We 
recognize the difficult trade-offs involving short-term risk of fuel 
treatments versus long term benefits of those treatments in reducing 
risks and improving habitat. We recognize other current threats to the 
species, its habitat, and its prey, including effects of drought and 
climate change on habitat; the potential spread of a new competitor/
predator (the barred owl); and possible threats of disease.
    We conclude that the overall magnitude of threats to the California 
spotted owl does not rise to the level that requires the protections of 
the Act. We will continue to monitor the status and management of the 
species. We will continue to accept additional information and comments 
from all concerned governmental agencies, the scientific community, 
industry, or any other interested party concerning this finding.

References Cited

    A complete list of all references cited is available on request 
from the Sacramento Fish and Wildlife Office (see ADDRESSES above).


    The primary authors of this document are Phil Detrich of the Yreka 
Fish Wildlife Office, Kenneth Sanchez of the Sacramento Fish and 
Wildlife Office, and Darrin Thome of the Ventura Fish and Wildlife 


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

    Dated: February 7, 2003.
Steve Williams,
Director, Fish and Wildlife Service.
[FR Doc. 03-3519 Filed 2-13-03; 8:45 am]