scholarly journals Influence of Habitat Fragmentation on Spotted owl Site Selection, Site Occupancy, and Reproductive Status in Western Oregon

1989 ◽  
Vol 13 ◽  
pp. 241-242
Author(s):  
Joseph Meyer ◽  
Larry Irwin ◽  
Mark Boyce
Keyword(s):  
Site Selection ◽  
Site Occupancy ◽  
Timber Harvesting ◽  
Decision Makers ◽  
Checkerboard Pattern ◽  
Bureau Of Land Management ◽  
Spotted Owl ◽  
Strix Occidentalis ◽  
Spotted Owls ◽  
Strix Occidentalis Caurina

Currently there is little empirical evidence to guide decision makers on how to manage for viable populations of the Northern Spotted Owl (Strix occidentalis caurina) and how to decide what extent and what types of timber harvesting do not adversely affect Spotted Owls. In this ongoing study we are addressing some of the urgent research needs related to Spotted Owls by testing the null hypotheses that various forms of forest fragmentation do not affect (1) site selection, (2) site occupancy, or (3) reproductive success of Spotted Owls at sites within the Bureau of Land Management (BLM) checkerboard pattern of land ownership and management in Western Oregon.

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.

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

1990 ◽  
Vol 14 ◽  
pp. 193-198
Author(s):  
R. Gutierrez ◽  
Sarah Rinkevich
Keyword(s):  
Economic Cost ◽  
Term Survival ◽  
Spotted Owl ◽  
Strix Occidentalis ◽  
Spotted Owls ◽  
Northern Spotted Owl ◽  
Management Plans ◽  
Strix Occidentalis Caurina ◽  
Heated Debate

The recent listing of the Northern spotted owl (Strix occidentalis caurina) by the U.S. Fish and Wildlife Service as a threatened species (Federal Register 1990) raises heated debate concerning the long-term survival of the species and perceived economic cost to timber industry (Thomas et al. 1988). Long term studies of the owls's ecology are necessary to provide information needed for ecologically based management plans (Dawson et al. 1987). Much is already known about the natural and life history of the Northern spotted owl (Forsman et al. 1984, Gutierrez et al. 1984, Gutierrez 1985, Franklin et al. 1990) as well as the California subspecies (S. o. occidentalis) (Gutierrez and Pritchard 1990). In contrast, the Mexican spotted owl (S. o. Iucida) is the least studied of the three subspecies (Ganey and Balda 1989). It is known that this latter subspecies inhabits rocky canyonlands and coniferous forests in the southwestern United States and Mexico (Kertell1977, Wagner et al. 1982, Webb 1983, Johnson and Johnson 1985, Ganey 1988, and Skaggs 1988) but there are few published studies on its ecology and habitat needs (Ganey 1988). Also, the effects of human activities, such as recreation, on the Mexican subspecies are unclear, particularly in isolated habitats (Gutierrez 1985). Therefore, in 1989, we initiated a two year investigation of abundance and distribution of Mexican spotted owls in Zion National Park. This report summarizes our 1990 survey effort and research findings.

scholarly journals Redefining the Distributional Boundaries of the Northern and California Spotted Owls: Implications for Conservation

The Condor ◽  
2005 ◽  
Vol 107 (1) ◽  
pp. 182-187
Author(s):  
R. J. Gutiérrez ◽  
George F. Barrowclough
Keyword(s):  
Current Knowledge ◽  
Range Limits ◽  
Spotted Owl ◽  
Strix Occidentalis ◽  
Spotted Owls ◽  
Actual Range ◽  
Northern Spotted Owl ◽  
Strix Occidentalis Caurina ◽  
Conservation Plans ◽  
Area Of Protection

Abstract The Northern Spotted Owl (Strix occidentalis caurina) is listed as a threatened species. However, the range description given at the time of listing is inconsistent with the range delineation given by the American Ornithologists' Union checklist of North American birds. Despite the quandary that this inconsistency represents regarding the area of protection afforded the Northern Spotted Owl, the range used in listing is consistent with the actual range suggested by mtDNA haplotypes diagnostic for the subspecies. The range description used in the listing decision of the Northern Spotted Owl and in many conservation plans have been repeated through time without a formal revision or basis for support. Based on current knowledge of Spotted Owl locations we revise the range limits for both Northern and California (S. o. occidentalis) Spotted Owls. Redefinición de los Límites de las Distribuciones de Strix occidentalis caurina y S. o. occidentalis: Implicaciones para Conservación Resumen. La lechuza Strix occidentalis caurina se considera amenazada. Sin embargo, la descripción de su rango de distribución hecha al momento en que fue incluida en la lista de especies amenazadas es inconsistente con la delimitación de su rango hecha por la lista de chequeo de aves de Norte América de la American Ornithologists' Union. A pesar de la incertidumbre que esta inconsistencia representa con respecto al área de protección con que cuenta S. o. caurina, el rango empleado al incluirla en la lista es consistente con el rango real sugerido por haplotipos de ADN mitocondrial diagnósticos para esta subespecie. La descripción del rango de distribución empleada para tomar la decisión de incluir a S. o. caurina en la lista de aves amenazadas y para muchos planes de conservación ha sido repetida a través del tiempo sin una revisión formal fundamentada. Con base en el conocimiento actual, en este estudio revisamos los límites de los rangos de S. o. caurina y de la subespecie de California, S. o. occidentalis.

scholarly journals Evidence for recent population bottlenecks in northern spotted owls (Strix occidentalis caurina)

2009 ◽  
Vol 11 (3) ◽  
pp. 1013-1021 ◽  
Author(s):  
W. Chris Funk ◽  
Eric D. Forsman ◽  
Matthew Johnson ◽  
Thomas D. Mullins ◽  
Susan M. Haig
Keyword(s):  
Population Bottlenecks ◽  
Strix Occidentalis ◽  
Spotted Owls ◽  
Strix Occidentalis Caurina ◽  
Northern Spotted Owls

Reply to the comment by Franklin et al. on “Are survival rates for northern spotted owls biased?”Appears in Can. J. Zool. 83: 1386–1390.

2006 ◽  
Vol 84 (9) ◽  
pp. 1380-1382
Author(s):  
Craig Loehle ◽  
Larry Irwin
Keyword(s):  
Mortality Rate ◽  
Recent Work ◽  
Survival Rates ◽  
Mortality Rates ◽  
The Body ◽  
Strix Occidentalis ◽  
True Value ◽  
Spotted Owls ◽  
Strix Occidentalis Caurina ◽  
Northern Spotted Owls

We reply to Franklin et al.’s critique of our recent work in which we computed survival for northern spotted owls ( Strix occidentalis caurina (Merriam, 1898)) from sites in western Oregon and northern California based on 197 radio-collared owls. Several methods gave similar results and we noted that our estimated survival rates might be closer to the true value than those derived from mark–recapture studies. We included an errant reference to Anthony et al. (Wildl. Monogr. No. 163, pp. 1–47 (2006)) in comments about bias in prior estimates of survival and hence of λ, a mistake for which we published an erratum. In spite of our erratum, Franklin et al. correct our presumed misunderstanding of the re-parameterized Jolly–Seber methods used in the article by Anthony et al. We never intended our comments to refer to the article by Anthony et al. The commentary also states that we overestimated survival because birds that left the study area might actually have died simultaneously with radio-collar destruction. However, in our earlier paper, we stated quite clearly that the fate of virtually every bird was accounted for by tracking them down if they left the study area or until the body was found if dead. They secondarily state that birds that emigrated might have a higher mortality rate and cited as evidence a study based on four owls. We do not consider that study sufficient to determine whether mortality rates for emigrating owls may be elevated. We also dispute several other criticisms but concur with them that several issues related to owl demography could benefit from further study.

Influence of prey abundance on northern spotted owl reproductive success in western Oregon

2003 ◽  
Vol 81 (10) ◽  
pp. 1715-1725 ◽  
Author(s):  
Daniel K Rosenberg ◽  
Keith A Swindle ◽  
Robert G Anthony
Keyword(s):  
Reproductive Success ◽  
Temporal Variability ◽  
Life History Strategy ◽  
Prey Abundance ◽  
Deer Mice ◽  
Spotted Owl ◽  
Strix Occidentalis ◽  
Flying Squirrels ◽  
Northern Spotted Owl ◽  
Strix Occidentalis Caurina

The hypothesis that high temporal variability of northern spotted owl (Strix occidentalis caurina) reproductive success is a response to prey abundance remains largely untested. We evaluated this relationship in the Oregon Cascade Mountains. Despite similar biomass of northern flying squirrels (Glaucomys sabrinus) (169 ± 13.9 g/ha) and deer mice (Peromyscus maniculatus) (160 ± 18.8 g/ha), flying squirrels dominated the breeding season diet based on both biomass (49%) and numbers (40%). Abundance of flying squirrels and western red-backed voles (Clethrionomys californicus) was more variable spatially ([Formula: see text]38% of process variation) than temporally (15%–24%), whereas abundance of deer mice was more similar across stands (12% spatial variation) than among years (68% temporal variation). Spotted owl reproductive success was statistically associated only with the abundance of deer mice (number of young per territory: r2 = 0.68). However, deer mice comprised only 1.6 ± 0.5% of the biomass consumed. The low temporal variability of the dominant prey species provided evidence that simple prey relationship models were not likely to explain the highly synchronous and temporally dynamic patterns of spotted owl reproductive performance. Reproductive success was likely a result of the interaction of both weather and prey and the life history strategy of this long-lived owl.

scholarly journals HELMINTH PARASITES OF NORTHERN SPOTTED OWLS (STRIX OCCIDENTALIS CAURINA) FROM OREGON

1989 ◽  
Vol 25 (2) ◽  
pp. 246-251 ◽  
Author(s):  
E. P. Hoberg ◽  
G. S. Miller ◽  
E. Wallner-Pendleton ◽  
O. R. Hedstrom
Keyword(s):  
Helminth Parasites ◽  
Strix Occidentalis ◽  
Spotted Owls ◽  
Strix Occidentalis Caurina ◽  
Northern Spotted Owls
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