Population Dynamics of the California Spotted Owl (Strix occidentalis occidentalis): A Meta-Analysis

Abstract Spotted Owls (Strix occidentalis) are territorial, generally nonmigratory, and strongly philopatric. Nevertheless, California Spotted Owls (S. o. occidentalis) exhibited breeding dispersal during 7% of interannual observations of banded individuals (n = 54 of 743 occasions). Based on ecological theory and published literature, we made a priori predictions about the factors associated with the probability of breeding dispersal and breeding dispersal distance, and about the consequences of dispersal. Breeding dispersal probability was higher for younger owls, single owls, paired owls that lost their mates, owls at lower quality sites, and owls that failed to reproduce in the year preceding dispersal. Sex had little effect on the probability of breeding dispersal. Dispersal distance was similar for female and male owls (median = 7 km, range = 1–33 km). We found no strong relationships between dispersal distance and any of the conditions that were associated with the probability of breeding dispersal. Dispersal resulted in improved territory quality in 72% of cases. These results indicate that breeding dispersal was condition-dependent and adaptive.

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Whole-genome sequences suggest long term declines of spotted owl (Strix occidentalis) (Aves: Strigiformes: Strigidae) populations in California

10.1101/343434 ◽

2018 ◽

Author(s):

Zachary R. Hanna ◽

John P. Dumbacher ◽

Rauri C.K. Bowie ◽

Jeffrey D. Wall

Keyword(s):

Isolation By Distance ◽

Whole Genome ◽

Population Declines ◽

Effective Population ◽

Spotted Owl ◽

Strix Occidentalis ◽

Genome Data ◽

Population Sizes ◽

California Spotted Owl

AbstractWe analyzed whole-genome data of four spotted owls (Strix occidentalis) to provide a broad-scale assessment of the genome-wide nucleotide diversity across S. occidentalis populations in California. We assumed that each of the four samples was representative of its population and we estimated effective population sizes through time for each corresponding population. Our estimates provided evidence of long-term population declines in all California S. occidentalis populations. We found no evidence of genetic differentiation between northern spotted owl (S. o. caurina) populations in the counties of Marin and Humboldt in California. We estimated greater differentiation between populations at the northern and southern extremes of the range of the California spotted owl (S. o. occidentalis) than between populations of S. o. occidentalis and S. o. caurina in northern California. The San Diego County S. o. occidentalis population was substantially diverged from the other three S. occidentalis populations. These whole-genome data support a pattern of isolation-by-distance across spotted owl populations in California, rather than elevated differentiation between currently recognized subspecies.

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Temporal Variation in the Vital Rates of an Insular Population of Spotted Owls (Strix Occidentalis Occidentalis): Contrasting Effects of Weather

The Auk ◽

10.1093/auk/121.4.1056 ◽

2004 ◽

Vol 121 (4) ◽

pp. 1056-1069

Author(s):

William S. LaHaye ◽

Guthrie S. Zimmerman ◽

R. J. Gutiérrez

Keyword(s):

Temporal Variation ◽

Breeding Season ◽

Process Variation ◽

Meta Analysis ◽

First Year ◽

Spotted Owl ◽

Strix Occidentalis ◽

Adult Females ◽

Temporal Process ◽

Spotted Owls

Abstract We studied the demography of an insular California Spotted Owl (Strix occidentalis occidentalis) population in southern California for 12 years. We used model selection based on information theory to examine the relationship between weather and reproduction and survival. Mean annual fecundity was 0.139 (SE = 0.050) for subadult females and 0.345 (SE = 0.028) for adult females. Adult females had higher fecundity than subadult females during all years, and fecundity in both age classes was higher when a wet year preceded a dry spring (i.e. breeding season). A model incorporating these factors explained 100% of the estimated temporal process variation in fecundity. Mean apparent survival was 0.796 (SE = 0.012), 0.880 (SE = 0.041), 0.692 (SE = 0.062), and 0.368 (SE = 0.038) for adult, second-year subadult, first-year subadult, and juvenile (first-year) owls, respectively. We found no temporal process variation in survival. Using a Leslie projection matrix, we estimated the finite rate of population change to be 0.906 (SE = 0.018) over the entire period of study (1987–1998), which indicated that the population declined ≈9% per year during the study. That rate of decline was higher than a rate (λ1991–1998 = 0.921, SE = 0.020) we estimated for a shorter period (1991–1998) that matched the time interval used in a recent meta-analysis of Spotted Owl population dynamics. We believe that both the present estimates and those of the meta-analysis are valid, given their respective goals. The study population was characterized by relatively high, constant survival of territorial birds, low and variable annual reproduction, and relatively low juvenile survival. Because weather was strongly correlated with reproduction, fecundity rates for the species may decline during short-term droughts and when storms occur during the breeding season. Weather extremes may not, however, be sufficient to affect temporal variation in survival of Spotted Owls in this part of their range.

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Demography of the California Spotted Owl in Northeastern California

The Condor ◽

10.1093/condor/103.4.667 ◽

2001 ◽

Vol 103 (4) ◽

pp. 667-677 ◽

Cited By ~ 3

Author(s):

Jennifer A. Blakesley ◽

Barry R. Noon ◽

Daniel W. H. Shaw

Keyword(s):

Population Change ◽

Adult Survival ◽

Apparent Survival ◽

Finite Rate ◽

Spotted Owl ◽

Strix Occidentalis ◽

Spotted Owls ◽

Female Survival ◽

California Spotted Owl ◽

Rate Of Decline

Abstract We estimated age-specific survival (ϕ), fecundity (b), and the finite rate of population change (λ) of California Spotted Owls (Strix occidentalis occidentalis) over a 10-year period (1990–1999). Two hundred nineteen juvenile and 200 subadult or adult owls were banded at 90 sites, with a combined total of 1080 captures. Least-squares mean estimates (± SE) of fecundity (# female fledglings per territorial female) over all years were 0.065 ± 0.066 for subadults (n = 33) and 0.291 ± 0.065 for adults (n = 381). Estimated annual apparent survival probability was 0.333 ± 0.055 for juveniles and 0.827 ± 0.015 for subadults and adults combined. Using these estimates to construct a four-stage projection matrix, the finite rate of population change, λ̂, was 0.910 ± 0.025. This value of λ suggests an annual rate of decline in the territorial population of 9% per year over the period of study. Elasticity analyses showed λ to be most sensitive to variation in adult female survival. However, the standard deviation of λ was dominated by year-to-year variation in fecundity. Conservation guidelines should focus on management activities that increase the value of adult survival while minimizing its temporal variability. Demografía de Strix occidentalis occidentalis en el Noreste de California Resumen. Estimamos la supervivencia (ϕ) y fecundidad (b) específicas por edad y la tasa discreta de crecimiento poblacional (λ) de Strix occidentalis occidentalis en un periodo de 10 años (1990–1999). Marcamos 219 lechuzas jóvenes y 200 adultas y subadultas en 90 localidades, para un total combinado de 1080 capturas. La estimación de la media (± ES) de fecundidad (número de pichones hembras por hembra territorial) fue 0.065 ± 0.066 en subadultos (n = 33) y 0.291 ± 0.065 en adultos (n = 381). La probabilidad estimada de supervivencia aparente fue 0.333 ± 0.055 para los jóvenes y 0.827 ± 0.015 para subadultos y adultos combinados. Usando tales estimaciones para construir una matriz de proyección de cuatro etapas, se obtiene una tasa discreta de cambio en la población, λ̂, de 0.910 ± 0.025. Este valor de λ indica una tasa anual decreciente del 9% en la población territorial durante el periodo estudiado. Los análisis de elasticidad indicaron que λ es más susceptible a la variación en la supervivencia de las hembras adultas. Sin embargo, la desviación medio de λ fue dominada por la variación interanual en la fecundidad. Las reglas de conservación deben concentrarse en actividades de manejo dirigidas a aumentar el nivel de supervivencia de hembras adultas y al mismo tiempo minimizar su variabilidad en el tiempo.

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California Spotted Owl (Strix occidentalis occidentalis) habitat use patterns in a burned landscape

The Condor ◽

10.1650/condor-16-184.1 ◽

2017 ◽

Vol 119 (3) ◽

pp. 375-388 ◽

Cited By ~ 15

Author(s):

Stephanie A. Eyes ◽

Susan L. Roberts ◽

Matthew D. Johnson

Keyword(s):

Habitat Use ◽

Spotted Owl ◽

Strix Occidentalis ◽

Use Patterns ◽

California Spotted Owl

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Spotted Owl (Strix occidentalis)

10.2173/bna.spoowl.02 ◽

1995 ◽

Author(s):

R. J. Gutiérrez ◽

A. B. Franklin ◽

W. S. Lahaye

Keyword(s):

Spotted Owl ◽

Strix Occidentalis

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Microsatellite markers for the Mexican spotted owl (Strix occidentalis lucida)

Molecular Ecology Notes ◽

10.1046/j.1471-8286.2002.00267.x ◽

2002 ◽

Vol 2 (4) ◽

pp. 446-448 ◽

Cited By ~ 20

Author(s):

Anna B. Thode ◽

Mary Maltbie ◽

Leslie A. Hansen ◽

Lance D. Green ◽

Jonathan L. Longmire

Keyword(s):

Microsatellite Markers ◽

Spotted Owl ◽

Strix Occidentalis ◽

Strix Occidentalis Lucida

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Food supplementation and abundance estimation in the white-footed mouse

Canadian Journal of Zoology ◽

10.1139/z06-101 ◽

2006 ◽

Vol 84 (8) ◽

pp. 1210-1215 ◽

Cited By ~ 2

Author(s):

Pei-Jen L. Shaner

Keyword(s):

Population Dynamics ◽

Food Availability ◽

Robust Design ◽

Meta Analysis ◽

Design Model ◽

Food Supplementation ◽

Abundance Estimates ◽

Abundance Indices ◽

Consumer Population ◽

White Footed Mouse

Food availability often drives consumer population dynamics. However, food availability may also influence capture probability, which if not accounted for may create bias in estimating consumer abundance and confound the effects of food availability on consumer population dynamics. This study compared two commonly used abundance indices (minimum number alive (MNA) and number of animals captured per night per grid) with an abundance estimator based on robust design model as applied to the white-footed mouse ( Peromyscus leucopus (Rafinesque, 1818)) in food supplementation experiments. MNA consistently generated abundance estimates similar to the robust design model, regardless of food supplementation. The number of animals captured per night per grid, however, consistently generated lower abundance estimates compared with MNA and the robust design model. Nevertheless, the correlations between abundance estimates from MNA, number of animals captured, and robust design model were not influenced by food supplementation. This study demonstrated that food supplementation is not likely to create bias among these different measures of abundance. Therefore, there is a great potential for conducting meta-analysis of food supplementation effect on consumer population dynamics (particularly in small mammals) across studies using different abundance indices and estimators.

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