Effects of Experimental Removal of Barred Owls on Population Demography of Northern Spotted Owls in Washington and Oregon PDF Download
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Author: J. David Wiens
Publisher:
ISBN:
Category : Barred owl
Languages : en
Pages : 0
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Book Description
Evidence indicates that competition with newly established barred owls (Strix varia) is causing rapid declines in populations of northern spotted owls (Strix occidentalis caurina), and that the long-term persistence of spotted owls may be in question without additional management intervention. A pilot study in California showed that lethal removal of barred owls in combination with habitat conservation may be able to slow or even reverse population declines of spotted owls at local scales, but it remains unknown whether similar results can be obtained in larger areas with different forest conditions and where barred owls are more abundant. In 2015, we implemented a before-after-control-impact (BACI) experimental design on two study areas in Oregon and Washington with at least 20 years of pre-treatment demographic data on spotted owls to determine if removal of barred owls can improve population trends of spatially associated spotted owls. Here we provide an overview of our research accomplishments and preliminary results in Oregon and Washington in 2015.
Author: J. David Wiens
Publisher:
ISBN:
Category : Barred owl
Languages : en
Pages : 0
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Book Description
Evidence indicates that competition with newly established barred owls (Strix varia) is causing rapid declines in populations of northern spotted owls (Strix occidentalis caurina), and that the long-term persistence of spotted owls may be in question without additional management intervention. A pilot study in California showed that lethal removal of barred owls in combination with habitat conservation may be able to slow or even reverse population declines of spotted owls at local scales, but it remains unknown whether similar results can be obtained in larger areas with different forest conditions and where barred owls are more abundant. In 2015, we implemented a before-after-control-impact (BACI) experimental design on two study areas in Oregon and Washington with at least 20 years of pre-treatment demographic data on spotted owls to determine if removal of barred owls can improve population trends of spatially associated spotted owls. Here we provide an overview of our research accomplishments and preliminary results in Oregon and Washington in 2015.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 480
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Book Description
Author: J. David Wiens
Publisher:
ISBN:
Category : Barred owl
Languages : en
Pages : 23
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Book Description
Author: J. David Wiens
Publisher:
ISBN:
Category : Barred owl
Languages : en
Pages : 23
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Book Description
Author: J. David Wiens
Publisher:
ISBN:
Category : Barred owl
Languages : en
Pages : 17
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Book Description
Author: Eric Forsman
Publisher: Univ of California Press
ISBN: 0520950593
Category : Science
Languages : en
Pages : 119
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Book Description
The Northern Spotted Owl, a threatened species that occurs in coniferous forests in the western United States, has become a well-known environmental symbol. But how is the owl actually faring? This book contains the results of a long-term effort by a large group of leading researchers to document population trends of the Northern Spotted Owl. The study was conducted on 11 areas in the Pacific Northwest from 1985 to 2008, and its objectives were both to evaluate population trends and to assess relationships between reproductive rates and recruitment of owls and covariates such as weather, habitat, and the invasion of a closely related species, the Barred Owl. Among other findings, the study shows that fecundity was declining in five populations, stable in three, and increasing in three areas. Annual apparent survival rates of adults were declining in 10 out of 11 areas. This broad, synthetic work provides the most complete and up-to-date picture of the population status of this inconspicuous forest owl, which is at the center of the complex and often volatile debate regarding the management of forest lands in the western United States. Researchers: Steven H. Ackers Lawrence S. Andrews David R. Anderson Robert G. Anthony Brian L. Biswell Kenneth P. Burnham Peter C. Carlson Raymond J. Davis Lowell V. Diller Katie M. Dugger Eric D. Forsman Alan B. Franklin Elizabeth M. Glenn Scott A. Gremel Dale R. Herter J. Mark Higley James E. Hines Robert B. Horn Joseph B. Lint James D. Nichols Janice A. Reid James P. Schaberl Carl J. Schwarz Thomas J. Snetsinger Stan G. Sovern Gary C. White
Author: U.S. Fish and Wildlife Service. Oregon Fish and Wildlife Office
Publisher:
ISBN:
Category : Barred owl
Languages : en
Pages : 396
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Book Description
Author: Elizabeth G. Kelly
Publisher:
ISBN:
Category : Animal migration
Languages : en
Pages : 156
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Book Description
Since their range expansion into the Pacific Northwest, anecdotal evidence suggests that northern barred owls (Strix varia varia) may be displacing northern spotted owls (Strix occidentalis caurina). My objectives were to characterize barred owl distribution and population increase in Oregon, investigate spotted owl territory performance before and after barred owl detection, and document cases of hybridization between barred owls and spotted owls. Between 1974-1998, 706 unique barred owl territories were reported in Oregon. At five spotted owl demographic study areas in Washington and Oregon, barred owl detections increased rapidly between 1987-1999. After barred owls were detected within 0.80 km of the spotted owl territory center, occupancy of spotted owls declined, and there was a significant likelihood of spotted owl displacement when barred owls were either currently or previously present. When barred owls were detected between 0.81-2.40 km from the spotted owl territory center, there was no difference in mean occupancy of spotted owls after barred owls were detected, and spotted owl detection rates when barred owls were currently or previously present were not significantly different from territories without barred owls. There was no effect on spotted owl reproductive performance after barred owls were detected within 0.80 km or between 0.8 1-2.40 km of the territory center. When barred owls were detected within 0.80 km of a spotted owl territory center, 46% of the spotted owls moved> 0.80 km and 39% were never found again. In comparison, at territories without barred owls, only 21% of spotted owls moved> 0.80 km, and only 11% disappeared completely. When barred owls were detected between 0.81-2.40 km from the territory center there was no difference in rates of movement or disappearance of spotted owls between territories with and without barred owls. Reports of hybridization between spotted owls and barred owls are uncommon. Between 1974 and 1999, 24 adult and 26 juvenile hybrids were confirmed in Washington and Oregon. Data from this study suggest that barred owls pose a threat to spotted owls but it is too soon to predict whether trends observed in this study will continue, or will spread to other areas.
Author: U.S. Fish and Wildlife Service
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Robert Gene Anthony
Publisher:
ISBN:
Category : Northern spotted owl
Languages : en
Pages : 52
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Book Description
"We analyzed demographic data from northern spotted owls (Strix occidentalis caurina) from 12 study areas in Washington, Oregon, California for 1985-2003. The purpose of our analyses was to provide an assessment of the status and trends of northern spotted owl populations throughout most of their geographic range"--Page 2.
