Effects of experimental removal of barred owls on population demography of northern spotted owls in Washington and Oregon—2016 progress report

Open-File Report 2017-1040
Prepared in cooperation with U.S. Fish and Wildlife Service, Bureau of Land Management, and U.S. Forest Service
By: , and 

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Abstract

Evidence indicates that competition with invasive barred owls (Strix varia) is causing rapid declines in populations of northern spotted owls (S. 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 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 areas with different forest conditions and a greater density of barred owls. In 2015, we implemented a before-after-control-impact (BACI) experimental design on three 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 localized population trends of spotted owls. Here, we report on research accomplishments and preliminary results from the first 21 months (March 2015–December 2016) of the planned 5-year experiment.

Suggested Citation

Wiens, J.D., Dugger, K.M., Lewicki, K.E., and Simon, D.C., 2017, Effects of experimental removal of barred owls on population demography of northern spotted owls in Washington and Oregon—2016 progress report: U.S. Geological Survey Open-File Report 2017-1040, 23 p., https://doi.org/10.3133/ofr20171040.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Background and Study Objectives
  • Experimental Study Areas
  • Methods
  • Preliminary Results, March 2015–December 2016
  • Associated Research Activities
  • Summary
  • Schedule to Completion
  • Acknowledgments
  • References Cited
  • Appendixes A–D

Additional publication details

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—2016 progress report
Series title Open-File Report
Series number 2017-1040
DOI 10.3133/ofr20171040
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Forest and Rangeland Ecosystem Science Center
Description iv, 23 p.
Country United States
State Oregon, Washington
Online Only (Y/N) Y
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