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Effects of experimental removal of barred owls on population demography of northern spotted owls in Washington and Oregon—2015 progress report

Open-File Report 2016-1041
By: , , , and 
https://doi.org/10.3133/ofr20161041

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Abstract

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 longterm 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-controlimpact (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.

Suggested Citation

Wiens, J.D., Dugger, K.M., Lewicki, K.E., and Simon, D.C., 2016, Effects of experimental removal of barred owls on population demography of northern spotted owls in Washington and Oregon—2015 progress report: U.S. Geological Survey Open-File Report 2016-1041, 16 p., http://dx.doi.org/10.3133/ofr20161041.

ISSN: 2331-1258 (online)

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Table of Contents

  • Abstract
  • Background and Study Objectives 
  • Experimental Study Areas 
  • Methods
  • Research Accomplishments and Preliminary Results 
  • Schedule to Completion
  • Acknowledgments
  • References Cited
  • Appendix A. Pre-Treatment Distribution of Territorial Pairs of Northern Spotted Owls and Barred Owls in Two Experimental Study Areas in Washington and Oregon, 2015
  • Appendix B. Model Selection Results for Single-Season Analysis of Proportion of Area Used and Detection Probability of Barred Owls in Two Experimental Study Areas in Washington and Oregon, 2015
  • Appendix C. Model Selection Results for an Analysis of Intensity of Use of Sample Plots and Unconditional Detection Probability of Barred Owls in Two Experimental Study Areas in Washington and Oregon, 2015
Publication type Report
Publication Subtype USGS Numbered Series
Title Effects of experimental removal of barred owls on population demography of northern spotted owls in Washington and Oregon—2015 progress report
Series title Open-File Report
Series number 2016-1041
DOI 10.3133/ofr20161041
Year Published 2016
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Forest and Rangeland Ecosystem Science Center
Description iv, 16 p.
Country United States
State Oregon, Washington
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details