Factors Influencing the Distribution of Northern Spotted Owls in the Eastern Cascades, Washington

2011 ◽  
Vol 92 (1) ◽  
pp. 19-36 ◽  
Author(s):  
Craig Loehle ◽  
Larry Irwin ◽  
John Beebe ◽  
Tracy Fleming
Keyword(s):  
Factors Influencing ◽  
Spotted Owls ◽  
Eastern Cascades ◽  
Northern Spotted Owls

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 Social status, forest disturbance, and Barred Owls shape long-term trends in breeding dispersal distance of Northern Spotted Owls

The Condor ◽  
2019 ◽  
Vol 121 (4) ◽  
Author(s):  
Julianna M A Jenkins ◽  
Damon B Lesmeister ◽  
Eric D Forsman ◽  
Katie M Dugger ◽  
Steven H Ackers ◽  
...  
Keyword(s):  
Forest Disturbance ◽  
Dispersal Distance ◽  
Historical Study ◽  
Breeding Dispersal ◽  
Spotted Owls ◽  
Dispersal Distances ◽  
Dispersal Events ◽  
Northern Spotted Owls ◽  
Barred Owls ◽  
Over Time

Abstract Dispersal among breeding sites in territorial animals (i.e. breeding dispersal) is driven by numerous selection pressures, including competition and spatiotemporal variation in habitat quality. The scale and trend of dispersal movements over time may signal changing conditions within the population or on the landscape. We examined 2,158 breeding dispersal events from 694 male and 608 female individually marked Northern Spotted Owls (Strix occidentalis caurina) monitored over 28 yr on 7 study areas to assess the relative importance of individual (sex, experience), reproductive (annual productivity, mate availability), and environmental (forest alteration, presence of competitor) sources of variation in breeding dispersal distance. Median breeding dispersal distance was 3.17 km, with 99% of all breeding dispersal events <37 km. Mean annual dispersal distances increased by 2.43 km in Oregon and 9.40 km in Washington between 1990 and 2017, which coincided with increases in annual detections of nonnative Barred Owl (S. varia). Frequency of breeding dispersal events, both among and within individuals, also increased over time. Female owls moved farther than males (median of 3.26 and 3.10 km, respectively), and birds with less experience (territory tenure) moved farther than those with more experience. Owls that were single in the year prior to dispersal moved 13–31% farther than those paired prior to dispersal. The greatest environmental change occurring over the course of our study was the expansion of Barred Owl populations. Breeding dispersal distance was positively related to Barred Owls in the study area and disturbance within the originating territory. While it appears that social factors continue to be important drivers of breeding dispersal distance in Spotted Owls, increased competition from Barred Owls and habitat alteration have a contributing effect. Increased breeding dispersal distances should be of concern for conservation efforts and considered in population monitoring because changing dispersal behavior may lead to higher rates of mortality and/or emigration from historical study areas.

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 Survival and Home-range Size of Northern Spotted Owls in Southwestern Oregon

2013 ◽  
Vol 47 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Jason W. Schilling ◽  
Katie M. Dugger ◽  
Robert G. Anthony
Keyword(s):  
Home Range ◽  
Home Range Size ◽  
Range Size ◽  
Spotted Owls ◽  
Northern Spotted Owls

scholarly journals Population trends in northern spotted owls: Associations with climate in the Pacific Northwest

2010 ◽  
Vol 143 (11) ◽  
pp. 2543-2552 ◽  
Author(s):  
Elizabeth M. Glenn ◽  
Robert G. Anthony ◽  
Eric D. Forsman
Keyword(s):  
Pacific Northwest ◽  
Population Trends ◽  
The Pacific ◽  
Spotted Owls ◽  
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.

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