Demography of the California Spotted 

Owl in the Sierra National Forest and 

Sequoia/Kings Canyon National Parks1 

George N. Steger,

2 Thomas E. Munton,2 Kenneth D. 

Johnson,2 and Gary P. Eberlein2 

Abstract 

Nine years (1990–1998) of demographic data on California spotted owls (Strix occidentalis 

occidentalis) in two study areas on the western slopes of the Sierra Nevada—one in the Sierra 

National Forest (SNF), the other in Sequoia/Kings Canyon National Parks (SNP)—are 

summarized. Numbers of territorial owls fluctuated from 85 to 50 in SNF and 80 to 58 in SNP 

over the period from 1990 to 1998, and demographic parameters indicate significantly 

declining populations in both study areas during the same period. Owl densities in conifer 

forests, reproductive performance, and survival rates did not differ significantly between the 

two study areas. These results suggest that factors influencing population trends may be 

more than local in scope, such as weather and/or prey populations. Local forest management 

may compound the regional variation, however, as may be reflected in the lower adult/ 

subadult survival rates in the SNF study area compared to the SNP study area. Continual 

timber harvest has occurred in SNF since the late 1800’s, but SNP has had little harvesting 

activity. Prescription burning and recreation continue to occur on both sites. Declining trends 

in owl numbers also reflect poor breeding success from 1995 through 1998, apparently 

attributable to unseasonal storms during the breeding period, especially during the incubation 

and nestling phases. Results suggest the hypothesis that spotted owls are “pulse” breeders 

that exhibit unusually successful reproduction only at intervals of several years, when all 

conditions are favorable. Continuation of these studies as part of the Kings River Sustainable 

Forest Ecosystems Project within boundaries of SNF will provide opportunities to explore 

relations among spotted owl demographics and timber harvest, weather, and prey availability. 

California spotted owls (Strix occidentalis occidentalis) in the western Sierra 

Nevada show a close association with dense forest and woodland ecosystems 

and their nesting/roosting stands typically have much “decadence” in the form 

of standing dead trees (snags), diseased and/or deformed live trees, and decaying 

wood on the forest floor. Pairs in Sierra conifer forests use home ranges that 

average about 3,400 acres during the breeding period and about 9,700 acres 

during the nonbreeding period (Verner and others 1992). Consequently, 

maintenance of sufficient habitat to assure viability of the Sierra population 

represents a substantial cost in allowable timber volume. The California spotted 

owl is not currently listed as a threatened or endangered species, although major 

environmental organizations are poised to petition the U.S. Fish and Wildlife to 

list the subspecies. 

Nests are typically in large trees—mean of about 45 inches in diameter at 

breast height (dbh)—with broken tops and cavities large enough to accommodate 

a female owl and two or three young (Steger and others 1997b). Nesting in the 

southern Sierra Nevada is intermittent, involving from none to as many as 95 

percent of pairs in any given year (50 percent of pairs nesting is regarded as a 

1 An abbreviated version of this paper 

was presented at the Symposium 

on the Kings River Sustainable 

Forest Ecosystems Project: Progress 

and Current Status, January 26, 

1998, Clovis, California. 

2 	Biological Technician, Wildlife 

Biologist, Wildlife Biologist, and 

Computer Specialist, respectively, 

Pacific Southwest Research Station, 

USDA Forest Service, 2081 E. Sierra 

Ave., Fresno, CA 93710. 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 107 
Steger, Munton, Johnson, Eberlein Demography of the California Spotted Owl in the Sierra National Forest and Sequoia/Kings Canyon National Parks 

“good” year). Details of the structure and composition of owl habitat in relation 

to successful breeding are still uncertain. 

The California spotted owl uses a diverse array of vegetation types, from 

riparian hardwood forests in the western Sierra Nevada foothills to red fir forests 

at high elevations. A recent technical assessment of the current status of the 

California spotted owl (Verner and others 1992) concluded that research is 

needed to distinguish levels of habitat quality for the birds by relating forest 

structure and composition to owl population parameters. 

This paper provides information on the California spotted owl’s adult 

survival rates, population turnover rates, reproductive rates, site fidelity, 

mate fidelity, and other population characteristics on two study sites under 

different management regimes, and it assesses the effects of management at 

landscape scales. 

The specific objectives of this study were to: 

• Estimate spotted owl density and territorial occupancy status by area. 

• Estimate vital rates (reproduction, mortality) by age class. 

• Assess site fidelity among individual spotted owls. 

• Estimate turnover rates (annual replacement of vacancies in occupied 

territories). 

• Estimate lambda (λ), the finite rate of population change under the null 

hypotheses, the population of resident owls is stable (λ = 1) in all study 

areas; and vital rates (age at first reproduction, reproductive rate, and 

survival rate) do not differ among years, between sexes, or between 

study sites. 

• Quantify the distribution of vegetation types within each study area. 

Study Areas 

The two study areas were selected for their proximity and vegetative similarities. 

The Sierra National Forest (SNF) study area, located in the southern Sierra 

Nevada about 30 mi east of Fresno, California, covered 160 mi2 from 1990 to 1993, 

when the area was enlarged to 265 mi2 as the Kings River Sustainable Forest 

Ecosystems Project began. The additional 105 mi2 was labeled the New Sierra 

(NS) study area. The 132-mi2 Sequoia and Kings Canyon National Parks study 

area (SNP) was also in the southern Sierra Nevada, about 50 mi east of Visalia, 

California. All three study areas included three habitat zones: 

• The oak-woodland type, at the lowest elevation—1,000 to 4,000 ft—had 

a canopy dominated by blue oak (Quercus douglasii), live oak (Quercus 

wislizenii), and foothill pine (Pinus sabiniana). Various foothill chaparral 

species were abundant. 

• The mid-elevation coniferous forest—4,000 to 8,000 ft—made up the 

majority of each study area. Vegetation was dominated by ponderosa 

pine (Pinus ponderosa), sugar pine (Pinus lambertiana), white fir (Abies 

concolor), incense cedar (Calocedrus decurrens), and black oak (Quercus 

kelloggii). Sites nearer to 8,000 ft had inclusions of Jeffrey pine (Pinus 

jeffreyi) and red fir (Abies magnifica). Nearly all of the SNF and NS sites 

had been logged since 1880, and only small, scattered patches of oldgrowth forest remain. Forest regeneration programs are in place on both 

public and private lands. Nearly all logging was some form of selective 

cutting; the little clear cutting that occurred was in scattered patches, 

typically smaller than 20 acres. The SNP included large stands of giant 

sequoia (Sequoiadendron giganteum) and large tracts of old-growth, 

108 USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 
 Demography of the California Spotted Owl in the Sierra National Forest and Sequoia/Kings Canyon National Parks 

mixed-conifer forest. Some logging occurred in the late 1800’s and early 

1900’s, but most stands were in mature or old stages of growth. 

• The high-elevation coniferous forest—8,000 to 9,600 ft—was dominated 

primarily by red fir, lodgepole pine (Pinus contorta), and western white 

pine (Pinus monticola). 

Methods 

These demographic studies involved surveying, banding, determining age and 

reproductive success, and rechecking owls on an annual basis from 1990 to 1998. 

Data from a few birds in the SNF study area included the period from 1987 

through 1989, when we were studying movements, home ranges, and vegetation 

types used by radio-tagged spotted owls. In addition, we have added information 

to the SNP database from birds studied in 1988 and 1989 by Roberts (1990) within 

boundaries of our SNP study area. Spotted owls were located by night and day 

surveys, by observers imitating calls of owls to elicit responses. Surveying 

included point, leapfrog road, walking cruise, and walk-in methods (Forsman 

1983). Survey period and the duration of surveys have been described by Steger 

and others (1993). 

Owl surveys in all study areas began in the first week of March each year and 

ended on 30 September. Changes in survey effort that occurred over time usually 

resulted from poor weather conditions or inability to access sites. Several changes 

in survey effort occurred in 1997 and 1998 because of budget constraints. We 

chose a system that provides survey priority to pair sites, then sites with past owl 

detections, and finally sites with no previous owl detections. Surveys continued 

from March through September or until funding was exhausted. 

Birds were captured with either a noose pole or mist net (Forsman 1983). All 

individuals were banded with a U.S. Fish and Wildlife Service leg band and a 

colored, plastic band on the opposite leg. A colored vinyl tab 0.8 inches long was 

attached to each color band (Franklin and others 1987), allowing hundreds of 

unique combinations. Sex and age classes of owls were determined following 

Forsman (1981, 1983). Fledgling, subadult, and adult age classes were recognized. 

Owls were assessed for social status, reproductive status, and turnover 

(replacement) on sites using standard techniques (Miller 1990). Protocols for 

determining these attributes were described by Steger and others (1993). 

Vegetative sampling was used to determine if nest sites differed in canopy 

cover, species composition, and size class between study areas. Nest trees were 

located from 1990 to 1998 using methods described by Forsman (1983), and 

sampled using methods described by Steger and others (1997a, 1997b). 

Data were analyzed by using a variety of statistical tests (Sokal and Rolf 

1981, Zar 1984). Annual survival rates (the probability of surviving from age x to 

x + 1) were calculated for subadults and adults combined as one age class using 

the Jolly-Seber (J-S) capture-recapture model for open populations (Jolly 1965; 

Seber 1965, 1982), which allows for losses and gains to the population between 

sampling periods. A sampling period was defined as one field season, for 

example from March 1 to September 30. The J-S model assumes that all 

individuals in the population have equal probabilities of survival, capture, and 

recapture (resighting in this case); that emigration is permanent, although the 

model partially adjusts for emigration vs. mortality using the rate at which 

emigrants return to the study area in later years; and that the sampling period is 

instantaneous (Nichols and others 1981, Seber 1982). A small percentage of our 

color-banded owls are more difficult to resight (read their band colors) than most 

banded owls because they tend to remain more concealed, and few have lost 

their colored bands. We consider these to be a minor violation of the first 

assumption. The second assumption is probably violated a few times because 

Steger, Munton, Johnson, Eberlein 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 109 
Steger, Munton, Johnson, Eberlein Demography of the California Spotted Owl in the Sierra National Forest and Sequoia/Kings Canyon National Parks 

not all emigrants from the study area are likely to return in later years. Finally, 

the third assumption is probably violated to a small degree because of the 

relatively long, 7-month sampling interval, although the very low mortality rate 

during this period mitigates this effect (Nichols and others 1981). 

We could not estimate juvenile survival rates for our study areas because of 

insufficient data. Instead, we have used 0.3278 as our estimate of juvenile survival 

rate, based on data from a similar demographic study of spotted owls in the San 

Bernardino Mountains, where probably few if any juveniles leave the study area 

(LaHaye and others 1997). 

Fecundity was calculated as the number of female offspring produced per 

territorial female checked for reproduction (Noon and others 1992). Turnover 

rates were calculated as the proportion of marked adults and subadults that were 

replaced annually on their territory by another owl. 

Lambda (λ) was calculated using the Lefkovitch stage-projection matrix 

model (Lefkovich 1965). Population trends were considered to be increasing if λ

>1.0, stable if λ = 1.0, and in decline if λ <1.0. An estimate of λ and its standard 

error allowed the tests of hypotheses: Ho

: λ >1, versus the alternative Ha: λ <1. 

The appropriate test statistics followed a Z-distribution, given by: Z = |( λ -1)/ 

λλ

|. We followed the method adopted by Noon and others (1992) in testing 

the significance of λ values, in which the appropriate test statistics followed a 

Z-distribution, and the specified probability of a Type I error = 0.05. 

Results 

Estimates of abundance, productivity, and population change, in most instances, 

were similar in the three study areas (table 1), although we consider the data for 

the NS study area to be marginal because it has been under study only since 1994. 

The numbers of territorial owls increased from 1991 through 1994 in SNF and 

1991 through 1995 in SNP, but they have since declined in all areas. Densities in 

the conifer forest zones (3,400-7,600 ft in SNF; 3,600-8,000 ft in SNP) did not differ 

significantly between SNF and SNP (t = 0.02; P = 0.98) but was considerably 

lower in NS. Productivity (young/pair) was marginally higher in SNF than in 

SNP, but turnover rates were lower in SNP (suggesting higher survival there). 

Although the average percentage of territorial birds disappearing each year was 

slightly higher in SNF than in SNP, the net loss of territorial birds (loss minus 

replacement rates) was essentially the same in those study areas. 

We have color banded 256 of 289 young owls known to fledge from the three 

study areas over the 9 years of study (129 of 140 fledglings in SNF, 108 of 128 in 

SNP, and 19 of 21 in NS). Of 242 fledglings banded prior to 1988, 42 (17 percent) 

have been recaptured within study area boundaries, another seven have been 

resighted but not recaptured, for an observed return rate of 20 percent. The 

fledgling sex ratio of 72:50 (male:female), determined from blood samples of 122 

birds from 1993 to 1998, was significantly different from a ratio of 1:1 (P = 0.0284, 

binomial test). (Note: the fledgling sex ratio in 1999 was 13:30, bringing the 

overall total to 85:80—not significantly different from 1:1.) 

Reproduction differed markedly among years. The percent of pairs fledging 

young averaged at least 45 percent in 1990-1994 in all study areas but less than 16 

percent in 1995-1998 (table 2). Generally, however, reproductive performance 

differed little among the study areas—when it was a “good” year in one area, it 

was good in all and, when it was a “bad” year in one area, it was bad in all. In 

most instances, poor reproduction was associated with unseasonably stormy 

weather in March, April, and/or May (North, “Environmental Factors Associated 

with Spotted Owl Reproduction,” this volume). 

Cumulative rates of population change (λ) from 1988 to 1998 were 

significantly less than 1 in all populations (table 1), indicating that all were 

110 USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 
 Demography of the California Spotted Owl in the Sierra National Forest and Sequoia/Kings Canyon National Parks Steger, Munton, Johnson, Eberlein 

Table 1—Measures of owl abundance, productivity, and population change on the three study areas 

Sierra New Sequoia/Kings 

National Sierra Canyon National Measure Forest Parks 

Most territorial owls 

(year) 

85.00 

(1990) 

37.00 

(1994) 

80.00 

(1995) 

Fewest territorial owls 

(year) 

50.00 

(1998) 

24.00 

(1998) 

58.00 

(1998) 

Mean number of pairs 28.30 12.80 27.50 

Mean number of owls/mi2 0.44 0.29 0.50 

Mean number of young/year 15.00 3.80 13.20 

Mean number of young/pair 0.62 0.33 0.58 

Mean survival rate of banded males 0.80 0.81 0.88 

Mean survival rate of banded females 0.80 0.87 0.86 

Mean annual percent of territorial 

owls moving to new territory in the 

study area 

6.00 3.00 3.00 

Mean loss rate (percent) of territorial 20.00 18.00 14.00 

owls 

Mean turnover rate (percent) of 

territorial owls1 

17.00 8.00 11.00 

Highest lambda value2 

(year) 

1.00 

(1993) 

1.04 

(1993) 

Lowest lambda value2 

(year) 

0.90 

(1998) 

0.95 

(1998) 

1 Turnover rate is the annual replacement rate of vacancies in territories. 

2 Too few years in the New Sierra study area to compute these values. 

Table 2—Percent of pairs sampled to established protocols that fledged young in the three study areas 

Year Sierra National Forest New Sierra Sequoia/Kings Canyon

National Parks

1990 72 — 88

1991 38 — 8

1992 87 — 85

1993 42 — 44

1994 42 45 48

1995 4 7 6

1996 12 8 7

1997 24 20 22

1998 10 20 27

USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 111 
Steger, Munton, Johnson, Eberlein 

Figure 1—Observed numbers of 

territorial California spotted owls 

compared to projected numbers, 

based on the numbers expected 

each year from 1990 through 1998 if 

the estimate of lambda (λ) is correct 

for the Sierra National Forest study 

area (λ = 0.90) and the Sequoia/ 

Kings Canyon National Parks study 

area (λ = 0.95). 

Demography of the California Spotted Owl in the Sierra National Forest and Sequoia/Kings Canyon National Parks 

declining. Projected rates of decline of the SNF and SNP populations, using the 

λ-values through 1998, exceeded those based on the known numbers of territorial 

birds in each population (fig. 1). 

Observed survival rates of banded males and females did not differ 

significantly (t = 1.96, P = 0.079; and t = 0.98, P = 0.35) between SNF and SNP. 

Among adult owls in the three study areas, males in SNF had the lowest mean 

annual survival rate (0.80 percent), and males in SNP had the highest (0.88 

percent) (table 1). These survival rates suggest that an original cohort population 

of 100 males in SNF might have a single individual survive to age 20; similarly a 

cohort of 100 males in SNP might have one surviving representative after 34 

years. In fact, some of the owls in our study areas are at least as old as the studies. 

A male banded as an adult in SNF in 1987 was still occupying a territory in 1998, 

giving it a minimum age of 14 years (an unbanded bird classified as an adult 

would be at least 3 years old), and a pair banded by Roberts (1990) as adults in 

SNP in 1989 were still in their territory in 1998, at a minimum age of 12 years. 

Discussion 

Population Trend 

The general picture emerging to date from the demographic studies of these 

spotted owl populations in the southern Sierra Nevada is puzzling and certainly 

warrants further study. The poor reproductive performance in 1995-1998 

appeared to result primarily from late seasonal storms that probably reduced the 

ability of males to deliver prey to their mates as they incubated eggs or brooded 

young. This interpretation is supported by the fact that reproductive failures 

occurred not only in SNF and NS but also in SNP, where owl habitats have not 

been altered by logging, and North (personal communication) found no 

difference between mean annual reproduction in SNF and SNP study areas. 

112 USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 
 Demography of the California Spotted Owl in the Sierra National Forest and Sequoia/Kings Canyon National Parks 

Further support comes from the fact that 9 of 11 owl pairs nesting in 1998 failed 

after an unusually powerful storm in May. 

In other years with unseasonal storms late in the winter or early spring, even 

when our sampling to full protocols indicated no nesting by a pair, we sometimes 

observed that the female had a brood patch, indicating that she had been 

incubating but deserted her nest. Because males provide food for the incubating 

female, and for her and the nestlings during the early part of the nestling period, 

a marked decline in his ability to capture and deliver prey to the nest site could 

force the female to leave the nest and forage for herself, thus jeopardizing the 

eggs or nestlings. 

It is a troubling fact that both the demographic data (λ) and the actual 

numbers of territorial birds indicate that all three study populations are declining. 

We believe, however, that our estimates of λ are negatively biased because 

permanent emigration of banded adults from a study area would lead to an 

underestimate of adult survival rate, and because our estimate of yearling 

survivorship also may be less than the true value. Consequently, we would 

expect population trajectories based on λ-values to be too steep, as we see in the 

comparison between those and empirical trajectories based on numbers of 

territorial birds (fig. 1). The difference in λ-values between study areas is 

attributable to higher adults/subadult survival rates in SNP than in SNF. 

Following the highly productive breeding season in 1992, the number of 

territorial owls increased in both SNF and SNP, reaching peak counts in 1994 and 

1995, respectively. This rise is consistent with the fact that most newly fledged 

spotted owls take 2-3 years to enter the territorial population. Declining numbers 

since then reflect the poor breeding years from 1995 to 1998. We should expect 

the number of territorial birds to increase markedly after the next productive 

nesting season. In this sense, we hypothesize that California spotted owls, at 

least in the southern Sierra Nevada, are “pulse” breeders, characterized by 

intermittent periods of unusually successful reproduction when all determining 

factors are favorable, but we would expect only moderate to poor success 

between pulses, depending on the mix of determining factors. This hypothesis 

not only fits our observations to date but also is consistent with the owl’s life 

history strategy, in particular its relatively low reproductive rate, its relatively 

long life span, and usually a delay in its age at first attempted reproduction. 

Relationship to Management 

Twenty-eight territories of California spotted owls are located within boundaries 

of the study area for the Kings River Sustainable Forest Ecosystems Project, and 

each has a protected activity center of about 300 acres set aside to protect the core 

area used by the owls. Over the course of the project, we expect to learn how 

these owls respond to the various silvicultural treatments within the two 32,000-

acre watersheds that comprise the study area. Controls for these “experimental” 

treatments will be available in the remaining 105,000 acres within boundaries of 

the demographic study areas in SNF and NS. An additional level of control is 

available in the 83,200-acre study area in SNP, where timber management is 

absent but prescribed fire and recreation occur. This study thus may provide 

some answers to some fundamental questions about the responses of spotted 

owls to timber harvesting and prescribed fire within their home ranges. 

Our current operating hypothesis is that successful breeding by the owls 

depends to a major extent on favorable weather conditions during the early 

stages of nesting—egg laying, incubation, and early nestling periods. Because we 

have experienced only 1 year (1992) when most pairs of owls in our study area 

nested, and the last 4 years (1995-1998) were poor for breeding by the owls, it 

may require a decade or two to fully understand the nature of the interacting 

factors needed to assure a self-sustaining population of spotted owls in 

ponderosa pine and mixed-conifer forest of the southern Sierra Nevada. 

Steger, Munton, Johnson, Eberlein 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 113 
Steger, Munton, Johnson, Eberlein Demography of the California Spotted Owl in the Sierra National Forest and Sequoia/Kings Canyon National Parks 

Acknowledgments 

Temporary field crews too numerous to name here have dedicated themselves to 

hard work in steep terrain at night, often during severe weather 

conditions, to help collect the data reported here. The study would have 

been impossible without their able and dedicated assistance over the past 

9 years. Gordon I. Gould, Jr., and Jared Verner provided constructive 

reviews of the draft manuscript. We deeply appreciated the contributions 

made by all of these persons. 

References 

Forsman, Eric D. 1981. Molt of the spotted owl. Auk 98: 735-742. 

Forsman, Eric D. 1983. Methods and materials for locating and studying spotted owls. Gen. Tech. 

Rep. PNW-162. Portland, OR: Pacific Northwest Forest and Range Experiment Station, Forest 

Service, U. S. Department of Agriculture; 8 p. 

Franklin, Alan B.; Ward, James P.; Gutiérrez, Ralph J. 1987. Population ecology of the northern 

spotted owl (Strix occidentalis caurina) in northwestern California: preliminary results, 1986. 

[Unpublished paper on file at the Forestry Sciences Laboratory, 2081 East Sierra Ave., Fresno, 

CA 93710.] 

Jolly, G. M. 1965. Explicit estimates from capture-recapture data with both death and 

immigration—stochastic model. Biometrika 52: 225-247. 

LaHaye, William S.; Leslie, Douglas G.; Gutiérrez, R. J. 1997. Big Bear spotted owl study, 1996. Final 

report to the Pacific Southwest Region (Region 5) USDA, Forest Service; 14 p. 

[Unpublished internal report on file at the Forestry Sciences Laboratory, 2081 East 

Sierra Ave., Fresno, CA 93710.] 

Lefkovich, L. P. 1965. The study of population growth in organisms grouped by stages. 

Biometrics 21: 1-18. 

Miller, Gary S. 1990. Standards and guidelines for establishment and implementation of 

demographic and density study areas for spotted owls. [Unpublished paper on file at the 

Forestry Sciences Laboratory, 2081 East Sierra Ave., Fresno, CA 93710.] 

Nichols, James D.; Noon, Barry R.; Stokes, S. Lynn; Hines, James E. 1981. Remarks on the use of 

mark-recapture methodology in estimating avian population size. In: Ralph, C. J.; Scott, J. M., 

eds. Estimating numbers of terrestrial birds. Cooper Ornithological Society. Studies in Avian 

Biology 6: 121-136. 

Noon, Barry R.; McKelvey, Kevin S.; Lutz, Daryl W.; LaHaye, William S.; Gutiérrez, R. J.; Moen, 

Christine A. 1992. Estimates of demographic parameters and rates of population change. In: 

Verner, Jared; McKelvey, Kevin S.; Noon, Barry R.; Gutiérrez, R. J.; Gould, Gordon I., Jr.; Beck, 

Thomas W., technical coordinators. 1992. The California spotted owl: a technical assessment of 

its current status. Gen. Tech. Rep. PSW-GTR-133. Berkeley, CA: Pacific Southwest Research 

Station, Forest Service, U.S. Department of Agriculture; 175-186. 

North, Malcolm. Ecologist, USDA Forest Service, Pacific Southwest Research Station, Forestry 

Sciences Laboratory, Fresno, CA. [Personal communication]. May 1999. 

Roberts, Cindy K. 1990. California spotted owls (Strix occidentalis occidentalis) inventory and 

demographic study, Sequoia and Kings Canyon National Parks. DFG-7525. Sacramento, CA: 

California Department of Fish and Game; 18 p. 

Seber, G. A. F. 1965. A note on the multiple recapture census. Biometrika 52: 249-259. 

Seber, G. A. F. 1982. The estimation of animal abundance and related parameters. 2d ed. New 

York, NY: Macmillan Co.; 654 p. 

Sokal, R. R.; Rohlf, F. J. 1981. Biometry. San Francisco. CA: W. H. Freeman and Co.; 859 p. 

Steger, George N.; Munton, Thomas E.; Verner, Jared. 1993. Preliminary results from a demographic 

study of spotted owls in Sequoia and Kings Canyon National Parks, 1990-1991. In: Veirs, 

Stephen D., Jr.; Stohlgren, Thomas J.; Schonewald-Cox, Christine, eds. Proceedings of the fourth 

conference on research in California’s National Parks. NPS/NRUC/NRTP-93/9. Davis, CA: 

Cooperative Park Studies Unit, University of California; 83-92. 

Steger, George N.; Eberlein, Gary P.; Munton, Thomas E.; Johnson, Kenneth D. 1997a. Characteristics 

of California spotted owl nest sites in foothill riparian and oak woodlands of the southern 

Sierra Nevada, California. In: Pillsbury, Norman H.; Verner, Jared; Tietje, William D., technical 

coordinators. Proceedings of a symposium on oak woodlands: ecology, management, and urban 

interface issues; 1996 March 19-22; San Luis Obispo, CA. Gen. Tech. Rep. PSW-GTR-160. Berkeley, 

CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; 355-364. 

114 USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 
 Demography of the California Spotted Owl in the Sierra National Forest and Sequoia/Kings Canyon National Parks 

Steger, George N.; Munton, Thomas E.; Johnson, Kenneth D.; Eberlein, Gary P. 1997b. Characteristics 

of nest trees and nest sites of California spotted owls in coniferous forests of the southern 

Sierra Nevada. 1997 Transactions of the Western Section of The Wildlife Society 33: 30-39. 

Verner, Jared; McKelvey, Kevin S.; Noon, Barry R.; Gutiérrez, R. J.; Gould, Gordon I., Jr.; Beck, 

Thomas W., technical coordinators. 1992. The California spotted owl: a technical assessment of 

its current status. Gen. Tech. Rep. PSW-GTR-133. Berkeley, CA: Pacific Southwest Research 

Station, Forest Service, U.S. Department of Agriculture; 285 p. 

Zar, Jerrold H. 1984. Biostatistical analysis. 2d ed. Englewood Cliffs, NJ: Prentice-Hall, Inc.; 718 p. 

Steger, Munton, Johnson, Eberlein 

USDA Forest Service Gen. Tech. Rep. PSW-GTR-183. 2002. 115 
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