scholarly journals Effects of barred owl (Strix varia) removal on population demography of northern spotted owls (Strix occidentalis caurina) in Washington and Oregon—2019 annual report

2020 ◽  
Author(s):  
J. David Wiens ◽  
Katie M. Dugger ◽  
Damon B. Lesmeister ◽  
Krista E. Dilione ◽  
David C. Simon
Keyword(s):  
Annual Report ◽  
Population Demography ◽  
Strix Occidentalis ◽  
Strix Varia ◽  
Spotted Owls ◽  
Strix Occidentalis Caurina ◽  
Northern Spotted Owls

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 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

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.

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.

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

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.

scholarly journals Variation in inbreeding rates across the range of Northern Spotted Owls (Strix occidentalis caurina): Insights from over 30 years of monitoring data

The Auk ◽  
2018 ◽  
Vol 135 (4) ◽  
pp. 821-833
Author(s):  
Mark P. Miller ◽  
Susan M. Haig ◽  
Eric D. Forsman ◽  
Robert G. Anthony ◽  
Lowell Diller ◽  
...  
Keyword(s):  
Monitoring Data ◽  
Strix Occidentalis ◽  
Spotted Owls ◽  
Strix Occidentalis Caurina ◽  
Northern Spotted Owls

Influence of primary prey on home-range size and habitat-use patterns of northern spotted owls (Strix occidentalis caurina)

1995 ◽  
Vol 73 (3) ◽  
pp. 433-439 ◽  
Author(s):  
Cynthia J. Zabel ◽  
Kevin McKelvey ◽  
James P. Ward Jr.
Keyword(s):  
Home Range ◽  
Prey Species ◽  
Home Range Size ◽  
Range Size ◽  
Home Ranges ◽  
Strix Occidentalis ◽  
Flying Squirrels ◽  
Spotted Owls ◽  
Strix Occidentalis Caurina ◽  
Northern Spotted Owls

Correlations between the home-range size of northern spotted owls (Strix occidentalis caurina) and proportion of their range in old-growth forest have been reported, but there are few data on the relationship between their home-range size and prey. The primary prey of spotted owls are wood rats and northern flying squirrels (Glaucomys sabrinus). Wood rats are larger and heavier than flying squirrels, and their population densities tend to be much greater than those of flying squirrels. We present data indicating that the home ranges of spotted owls are smaller where their diet consists predominantly of wood rats than where it consists predominantly of flying squirrels, and the proportion of the diet consisting of wood rats and flying squirrels explained significant variation in home-range size. We also found a significant correlation between home-range size and abundance of wood rats. These data indicate that prey species are a better predictor of home-range size than the proportion of older forest within spotted owl home ranges in the Klamath Province of northwestern California and southwestern Oregon, an area that is predominantly late-successional forest. Differences in habitat use were also related to prey species. Where spotted owls foraged for wood rats, the results indicated a preference for habitat edges, but where they utilized flying squirrels no such patterns were apparent.

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