scholarly journals Demography of the California Spotted Owl in Northeastern California

The Condor ◽  
2001 ◽  
Vol 103 (4) ◽  
pp. 667-677 ◽  
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.

scholarly journals Breeding Dispersal In the California Spotted Owl

The Condor ◽  
2006 ◽  
Vol 108 (1) ◽  
pp. 71-81 ◽  
Author(s):  
Jennifer A. Blakesley ◽  
David R. Anderson ◽  
Barry R. Noon
Keyword(s):  
A Priori ◽  
Dispersal Distance ◽  
Breeding Dispersal ◽  
Territory Quality ◽  
Spotted Owl ◽  
Factors Associated ◽  
Strix Occidentalis ◽  
Spotted Owls ◽  
California Spotted Owl ◽  
Dispersal Probability

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.

scholarly journals Does The Presence of Barred Owls Suppress the Calling Behavior of Spotted Owls?

The Condor ◽  
2006 ◽  
Vol 108 (4) ◽  
pp. 760-769 ◽  
Author(s):  
Michelle L. Crozier ◽  
Mark E. Seamans ◽  
R. J. GutiÉRrez ◽  
Peter J. Loschl ◽  
Robert B. Horn ◽  
...  
Keyword(s):  
Calling Behavior ◽  
Field Observations ◽  
Spotted Owl ◽  
Strix Occidentalis ◽  
Response Data ◽  
Strix Varia ◽  
Spotted Owls ◽  
Strix Occidentalis Caurina ◽  
Northern Spotted Owls ◽  
Barred Owls

Abstract Abstract Barred Owls (Strix varia) have expanded their range throughout the ranges of Northern (Strix occidentalis caurina) and California Spotted Owls (S. o. occidentalis). Field observations have suggested that Barred Owls may be behaviorally dominant to Spotted Owls. Therefore, we conducted a test of behavioral dominance by assessing responsiveness of Spotted Owls to conspecific calls when they were in the simulated presence (i.e., imitation of Barred Owl vocalizations) of a Barred Owl. We hypothesized that Spotted Owls would be less likely to respond to conspecific calls in areas where Barred Owls were common. We used a binary 2 × 2 crossover experimental design to examine male Spotted Owl responses at 10 territories randomly selected within two study areas that differed in abundance of Barred Owls. We also conducted a quasi experiment at four study areas using response data from any Spotted Owl (male or female) detected following exposure to Barred Owl calls. We inferred from the crossover experiment that the simulated presence of a Barred Owl might negatively affect Spotted Owl responsiveness. Both subspecies of Spotted Owl responded less to Spotted Owl calls after exposure to Barred Owl calls, Northern Spotted Owls responded less frequently in areas having higher numbers of Barred Owls, and California Spotted Owls responded less frequently than Northern Spotted Owls overall.

scholarly journals Are Barred Owls Displacing Spotted Owls?

The Condor ◽  
2003 ◽  
Vol 105 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Elizabeth G. Kelly ◽  
Eric D. Forsman ◽  
Robert G. Anthony
Keyword(s):  
Pacific Northwest ◽  
Current Status ◽  
Spotted Owl ◽  
Strix Occidentalis ◽  
Strix Varia ◽  
The Pacific ◽  
Spotted Owls ◽  
Before And After ◽  
Strix Occidentalis Caurina ◽  
Barred Owls

Abstract Barred Owls (Strix varia) have expanded their range into the Pacific Northwest, and anecdotal evidence suggests that they may be displacing the federally threatened Northern Spotted Owl (Strix occidentalis caurina). Our objectives were to describe the current status of Barred Owls in Oregon and compare occupancy of Spotted Owls in historic Spotted Owl territories before and after Barred Owls were first detected in those territories. Between 1974 and 1998, we estimated that 706 different Barred Owl territories were located in Oregon. From 1989–1998 an average of 60 new Barred Owl territories were located in Oregon each year. In Spotted Owl demographic study areas in Oregon and Washington, Barred Owl detections increased at Spotted Owl territories from 1987–1999. Occupancy of Spotted Owl territories declined after Barred Owls were detected within 0.80 km of the territory center. When Barred Owls were detected 0.81–2.40 km from Spotted Owl territory centers, occupancy of Spotted Owls was only marginally less than at territories without Barred Owls. This suggests that the frequency and intensity of interactions between the two species is negatively associated with distance between them. Our results suggest that land managers and regulatory agencies should regard Barred Owls as a threat to Spotted Owls, particularly if Barred Owls continue to increase in number as they have during the past 25 years. ¿Está Strix varia Desplazando a Strix occidentalis caurina? Resumen. Desde su expansión hacia el Pacífico Noroeste, existe evidencia anecdótica de que Strix varia podría estar desplazando a S. occidentalis caurina. Nuestros objetivos fueron describir el estatus actual de S. varia en Oregon y comparar la ocurrencia de S. occidentalis caurina en sus territorios históricos antes y después de que S. varia se detectó por primera vez en dichos territorios. Entre 1974 y 1998, estimamos que se confirmaron 706 territorios diferentes de S. varia en Oregon. Entre 1989 y 1998, se localizaron en promedio 60 nuevos territorios de S. varia anualmente. En áreas con estudios demográficos de S. occidentalis caurina en Oregon y Washington, las detecciones de S. varia en territorios de S. occidentalis caurina se incrementaron entre 1987 y 1999. En comparación con territorios sin S. varia, la ocupación de territorios de S. occidentalis caurina disminuyó luego de que se detectaron individuos de S. varia a menos de 0.80 km del centro del territorio. Cuando se detectaron individuos de S. varia entre 0.81 y 2.40 km del centro de los territorios, la ocupación de éstos fue sólo marginalmente menor que en territorios sin S. varia. Esto sugiere que la frecuencia e intensidad de la interacción entre las dos especies está asociada con la distancia entre ellas. Nuestros resultados sugieren que las autoridades ambientales y de regulación deben considerar a S. varia como una amenaza para S. occidentalis caurina, particularmente si los números de S. varia se siguen incrementando como en los últimos 25 años.

Comment on “Are survival rates for northern spotted owls biased?”Appears in Can. J. Zool. 83: 1386–1390.

2006 ◽  
Vol 84 (9) ◽  
pp. 1375-1379 ◽  
Author(s):  
A.B. Franklin ◽  
J.D. Nichols ◽  
R.G. Anthony ◽  
K.P. Burnham ◽  
G.C. White ◽  
...  
Keyword(s):  
Population Change ◽  
Survival Rates ◽  
Negative Bias ◽  
Strix Occidentalis ◽  
Spotted Owls ◽  
Strix Occidentalis Caurina ◽  
Capture Recapture ◽  
Northern Spotted Owls ◽  
Biased Estimates

Loehle et al. recently estimated survival rates from radio-telemetered northern spotted owls ( Strix occidentalis caurina (Merriam, 1898)) and suggested that survival rates estimated for this species from capture–recapture studies were negatively biased, which subsequently resulted in the negatively biased estimates of rates of population change (λ) reported by Anthony et al. (Wildl. Monogr. No. 163, pp. 1–47 (2006)) . We argue that their survival estimates were inappropriate for comparison with capture–recapture estimates because (i) the manner in which they censored radio-telemetered individuals had the potential to positively bias their survival estimates, (ii) their estimates of survival were not valid for evaluating bias, and (iii) the size and distribution of their radiotelemetry study areas were sufficiently different from capture–recapture study areas to preclude comparisons. In addition, their inferences of negative bias in rates of population change estimated by Anthony et al. were incorrect and reflected a misunderstanding about those estimators.

Realized population change for long-term monitoring: California spotted owl case study

2013 ◽  
Vol 77 (7) ◽  
pp. 1449-1458 ◽  
Author(s):  
Mary M. Conner ◽  
John J. Keane ◽  
Claire V. Gallagher ◽  
Gretchen Jehle ◽  
Thomas E. Munton ◽  
...  
Keyword(s):  
Population Change ◽  
Spotted Owl ◽  
Long Term Monitoring ◽  
California Spotted Owl ◽  
Term Monitoring

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

2004 ◽  
pp. 1-54 ◽  
Author(s):  
Alan B. Franklin ◽  
R. J. Gutiérrez ◽  
James D. Nichols ◽  
Mark E. Seamans ◽  
Gary C. White ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Meta Analysis ◽  
Spotted Owl ◽  
Strix Occidentalis ◽  
California Spotted Owl

scholarly journals Distribution and Abundance of Spotted Owls in Zion National Park

1989 ◽  
Vol 13 ◽  
pp. 226-233
Author(s):  
R. Gutierrez ◽  
Douglas Call ◽  
Sarah Rinkevich
Keyword(s):  
National Park ◽  
Spotted Owl ◽  
Brood Rearing ◽  
Strix Occidentalis ◽  
Nest Sites ◽  
Zion National Park ◽  
Spotted Owls ◽  
Fledgling Success ◽  
Strix Occidentalis Lucida ◽  
Mexican Spotted Owls

The main objective of this study is to estimate the distribution, habitat use, and reproductive status of Mexican spotted owls (Strix occidentalis lucida) in Zion National Park. This information will allow managers to coordinate park activities that potentially conflict with nest sites, roost sites, or brood rearing habitats. Other objectives of this study are to estimate spotted owl food habits and fledgling success, and to compare these findings with other North American spotted owl populations.

scholarly journals Mexican Spotted Owl (Strix Occidentalis) Population Dynamics: Influence of Climatic Variation on Survival and Reproduction

The Auk ◽  
2002 ◽  
Vol 119 (2) ◽  
pp. 321-334 ◽  
Author(s):  
Mark E. Seamans ◽  
R. J. Gutiérrez ◽  
Christopher A. May
Keyword(s):  
New Mexico ◽  
Reproductive Output ◽  
Monsoon Season ◽  
Life History Strategy ◽  
Climatic Variation ◽  
Spotted Owl ◽  
Strix Occidentalis ◽  
Spotted Owls ◽  
Survival And Reproduction ◽  
Strix Occidentalis Lucida

Abstract Understanding the mechanisms causing temporal variability in demographic parameters is essential to understanding fluctuations in populations. As part of a long-term demographic study, we evaluated influence of climate on Mexican Spotted Owl (Strix occidentalis lucida) annual survival and reproduction in two study areas, one in Arizona and one in New Mexico. Spotted Owl survival in New Mexico and reproductive output in both study areas were positively related to total amounts of precipitation from the previous year, previous winter, or monsoon season. For both study areas, temporal process variation in reproductive output (CV[R] = 51.2 and 75.2% for Arizona and New Mexico, respectively) was greater than that for survival (CV[ϕ] = 12.9 and 7.1% for Arizona and New Mexico, respectively). Precipitation from the previous year explained 73% of σ̂2temporal reproductive output for Arizona owls and precipitation from the previous monsoon explained 42% of σ̂2temporal in reproductive output for New Mexico owls. Precipitation from the previous monsoon season explained 53% of σ̂2temporal in Arizona owl survival and precipitation from the previous winter explained 56% of σ̂2temporal in New Mexico owl survival. The two populations of Spotted Owls we studied appeared to have the same life-history strategy hypothesized for a population of Northern Spotted Owls (S. o. caurina), although the Mexican subspecies apparently responded quite differently to climatic variation.

scholarly journals Management implications derived from long term re-sight data: annual survival of the Maui Parrotbill Pseudonestor xanthophrys

2013 ◽  
Vol 24 (3) ◽  
pp. 316-326 ◽  
Author(s):  
HANNA L. MOUNCE ◽  
KELLY J. IKNAYAN ◽  
DAVID L. LEONARD ◽  
KIRSTY J. SWINNERTON ◽  
JIM J. GROOMBRIDGE
Keyword(s):  
Management Strategies ◽  
Survival Rates ◽  
Adult Survival ◽  
Accurate Estimation ◽  
Limited Information ◽  
Adult Males ◽  
Apparent Survival ◽  
As Species ◽  
Female Survival ◽  
Species Specific

SummaryThe accurate estimation of key demographic parameters is invaluable for making decisions about the management of endangered wildlife but such estimates are often difficult to obtain. Parameters such as species-specific apparent survival rates are an important component in understanding population ecology and informing management decisions. The Maui Parrotbill Pseudonestor xanthophrys is a ‘Critically Endangered’ Hawaiian honeycreeper endemic to the Island of Maui. We used an 18-year encounter history dataset comprising 146 marked individuals to estimate apparent survival between sexes and age classes (juvenile, adult). A difference in survival rates between sexes was strongly supported; 0.72 ± 0.04 for adult females and 0.82 ± 0.03 for adult males. This difference may be a reflection of either reproductive costs or additional risks of incubation and brooding, such as depredation. We also found support for age-biased survival, but limited information for juveniles did not provide a well-supported model fit for our data (juvenile survival = 0.17 ± 0.15; adults = 0.78 ± 0.02). However, apparent adult survival was similar to that of other Hawaiian passerines (mean 0.78 ± 0.03, n = 16). These results suggest that efforts to prevent the extinction of this species may benefit from future management strategies focused on increasing female survival such as predator reduction.

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