Threat of Invasive Barred Owls to Northern Spotted Owls and their Habitats

Science Center Objects

As an apex predator and fiercely territorial invader, barred owls at high densities have the potential to affect a variety of native wildlife through competition, niche displacement, and predation. Such impacts may be especially problematic for conservation of the federally threatened northern spotted owl, whose populations have continued to decline despite widespread protection of old forest habitat for the owl and associated wildlife. We conduct research to address the implications of the barred owl range expansion to conservation of northern spotted owls and other native wildlife in the Pacific Northwest. We work closely with resource managers to provide information on the status and ecology of barred owls, their role in population declines of northern spotted owls, and effectiveness of management options.

Current and Recent Studies

Effects of Barred Owls on Population Demography of Spotted Owls

A clear understanding of how competition with newly established barred owls contributes to population declines of northern spotted owls is required to inform potential control, mitigation, and recovery strategies. In collaboration with US Fish & Wildlife Service we are using large-scale field experiments to determine whether removing barred owls from select areas can improve population trends of northern spotted owls. This research will provide a definitive answer to whether competition with barred owls is contributing to population declines of spotted owls, and if so, whether control of barred owl numbers is an ecologically practical and cost-effective management tool to consider in future conservation strategies for spotted owls. Please visit the USGS project website here.

Collaborators: U.S. Fish and Wildlife Service, Oregon State University, Colorado State University, The Hoopa Tribe, California Academy of Sciences

 

Predator-prey Interactions of a Non-native Raptor

Little research exists on the overall impacts of the barred owl, a newly established apex predator in the Pacific Northwest, on other forest species, besides spotted owls, and food-web dynamics. This project takes advantage of the experimental design associated with an on-going barred owl removal experiment to evaluate the impact this novel avian predator is having on the food web in Pacific Northwest forests. Understanding the impact of barred owls on the food web is critical for spotted owls and other native species, particularly as barred owl densities reach carrying capacity in these forests.

Collaborators: U.S. Fish and Wildlife Service

 

Anticoagulant Rodenticide Risk to Pacific Northwest Predators

Contamination of nontarget wildlife by anticoagulant rodenticides is a global conservation concern. Recent studies in remote forests of California have shown anticoagulant rodenticide contamination of the food web and transfer to sensitive forest predators, including the federally threatened northern spotted owl. The USGS is leading a team of scientists that are using barred owl carcasses to test if anticoagulant rodenticides pose a risk to the spotted owl and other old-forest wildlife in the Pacific Northwest. For information on a recent publication, click here.

Collaborators: U.S. Fish and Wildlife Service, Bureau of Land Management, U.S. Forest Service, University of California at Davis

 

Competitive Interactions and Resource Use

Understanding the competitive relationship between spotted owls and barred owls requires primary information on individual life-history traits, resource use, and population dynamics. This research investigates the distribution, habitat associations, diets, and demography of barred owls and spotted owls so that the potential mechanisms and consequences of interspecific competition can be identified and addressed within a management context.

Collaborators: U.S. Fish and Wildlife Service, U.S. Forest Service, National Park Service, Bureau of Land Management, Oregon Department of Forestry, Oregon State University, Boise State University, Colorado State University

 

Survey and Monitoring Tools for Barred Owls

Most information on occurrence and distribution of barred owls in the Pacific Northwest is limited to ancillary data from studies of spotted owls. Our research addresses this shortcoming by developing, testing, and implementing survey designs that allow researchers and land managers to monitor occurrence and distribution of barred owls with high confidence.

Collaborators: U.S. Fish and Wildlife Service, U.S. Forest Service, Oregon State University

 

Conservation Genetics of Spotted Owls

The USGS has been collecting and analyzing information about spotted owl genetics for decades. Management agencies use these and other genetic information to review the status of the northern spotted owl, and in combination with population estimates and habitat assessments, to consider management options for all three subspecies - California, northern, and Mexican - of spotted owl and their hybrids.

Collaborators: U.S. Fish and Wildlife Service, U.S. Forest Service, Oregon State University