image: Adult female northern spotted owl (Strix occidentalis caurina) in the Coast Range of western Oregon, USA. view more
Credit: Patrick S. Kolar (US Geological Survey, Washington, DC).
Researchers examine the long-term effects of removing invasive species from the US West Coast. Removing invasive species to decrease the risk of extinction of native species is common, but the long-term effects of such ecological restoration programs are unclear. Native to eastern North America, barred owls are considered an invasive species on the western coast of the United States, and their territorial competition with the region's northern spotted owls has led to the latter's population decline. Between 2002 and 2019, J. David Wiens and colleagues surveyed barred owls and spotted owls across five study areas in California, Oregon, and Washington. The authors compared owl populations before and after invasive barred owls underwent removal treatments. Removal of barred owls had a significant positive effect on the survival of spotted owls, having arrested spotted owl populations declines. The authors also detected an increase in spotted owls dispersing to territories upon barred owl removal from such locations. However, spotted owl populations continued declining rapidly in areas where barred owls did not undergo removal treatments. The findings suggest that controlling invasive barred owl populations may not only increase native spotted owl populations but also help conserve biodiversity across the Pacific Northwest, according to the authors.
Article #21-02859: "Invader removal triggers competitive release in a threatened avian predator," by J. David Wiens et al.
MEDIA CONTACT: J. David Wiens, US Geological Survey, Corvallis, Oregon; tel: 541-231-3654; email: jwiens@usgs.gov
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Journal
Proceedings of the National Academy of Sciences