Barred owls like this one were most strongly associated with patches of large hardwood and conifer trees in relatively flat areas along streams.
Threat of Invasive Barred Owls to Northern Spotted Owls and their Habitats Active
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
Below are other science projects associated with this project.
Effects of Experimental Removal of Barred Owls on Population Demography of Northern Spotted Owls in the Pacific Northwest
If you are unable to access a product or publication online, you can request a copy by sending an email with your contact information and the publication's citation to fresc_outreach@usgs.gov or call (541) 750-1030.
Anticoagulant rodenticide exposure in Barred Owls (Strix varia) collected in Washington and Oregon 2015-2017
Microsatellite markers, habitat quality, and sample location data for Northern Spotted Owls (Strix occidentalis caurina)
Northern spotted and barred owl pics.
Barred owls like this one were most strongly associated with patches of large hardwood and conifer trees in relatively flat areas along streams.
Northern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Northern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Spotted Owl flying
Spotted Owl flying
Northern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Northern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Northern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Northern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Barred owls (Strix varia) have expanded their geographic range from eastern to western North America. Their newly expanded range now completely overlaps that of the federally threatened northern spotted owl (S. occidentalis caurina).
Barred owls (Strix varia) have expanded their geographic range from eastern to western North America. Their newly expanded range now completely overlaps that of the federally threatened northern spotted owl (S. occidentalis caurina).
This Barred Owl was fearless in Baton Rouge, LA
This Barred Owl was fearless in Baton Rouge, LA
Barred owl perched. Species identification tentative.
Barred owl perched. Species identification tentative.
If you are unable to access a product or publication online, you can request a copy by sending an email with your contact information and the publication's citation to fresc_outreach@usgs.gov or call (541) 750-1030.
Range-wide sources of variation in reproductive rates of northern spotted owls
Anticoagulant rodenticides in Strix owls indicate widespread exposure in west coast forests
Effects of experimental removal of Barred Owls on population Demography of Northern Spotted Owls in Washington and Oregon—2018 Progress Report
Geographic variation in natal dispersal of Northern Spotted Owls over 28 years
Three-dimensional partitioning of resources by congeneric forest predators with recent sympatry
Barred owl research needs and prioritization in California
Isolation by distance versus landscape resistance: Understanding dominant patterns of genetic structure in Northern Spotted Owls (Strix occidentalis caurina)
Variation in inbreeding rates across the range of Northern Spotted Owls (Strix occidentalis caurina): Insights from over 30 years of monitoring data
Effects of experimental removal of Barred Owls on population demography of Northern Spotted Owls in Washington and Oregon—2017 progress report
Genetic differentiation and inferred dynamics of a hybrid zone between Northern Spotted Owls (Strix occidentalis caurina) and California Spotted Owls (S. o. occidentalis) in northern California
Integrating count and detection–nondetection data to model population dynamics
Effects of experimental removal of barred owls on population demography of northern spotted owls in Washington and Oregon—2016 progress report
News Releases and plain language summaries of some of our products.
These are our partners.
- Overview
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 OwlsThe 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
- Science
Below are other science projects associated with this project.
Effects of Experimental Removal of Barred Owls on Population Demography of Northern Spotted Owls in the Pacific Northwest
Barred owls ( Strix varia ) have expanded their geographic range from eastern to western North America, and their newly expanded range now completely overlaps that of the federally threatened northern spotted owl ( S. occidentalis caurina ; Gutiérrez et al. 2007, Livezey 2009, USFWS 2013). Evidence from long-term demographic studies indicates that the presence of barred owls has contributed... - Data
If you are unable to access a product or publication online, you can request a copy by sending an email with your contact information and the publication's citation to fresc_outreach@usgs.gov or call (541) 750-1030.
Anticoagulant rodenticide exposure in Barred Owls (Strix varia) collected in Washington and Oregon 2015-2017
This dataset includes anticoagulant rodenticide (AR) screening results of 40 Barred Owls (Strix varia) collected in forested landscapes of Washington and Oregon from 2015-2017. Liver tissue was collected from each owl and screened for exposure to eight AR compounds, including 4 first-generation ARs (warfarin, diphacinone, chlorophacinone, and coumachlor), and 4 second-generation ARs (brodifacoum,Microsatellite markers, habitat quality, and sample location data for Northern Spotted Owls (Strix occidentalis caurina)
The data are included in 8 separate text files: 1) "Sample_coordinates.txt". The file contains sample identifiers along with geographic coordinates associated with each sample. Coordinates are specified as UTM Zone 10 values (WGS84). 2) "Sample_genotypes.txt". The file contains a sample identifier along with microsatellite genotypes associated with each sample. 3) "uniform_conductances.asc". An - Multimedia
Northern spotted and barred owl pics.
Barred OwlBarred owls like this one were most strongly associated with patches of large hardwood and conifer trees in relatively flat areas along streams.
Barred owls like this one were most strongly associated with patches of large hardwood and conifer trees in relatively flat areas along streams.
Spotted owl (Strix occidentalis)Northern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Northern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Northern spotted OwlSpotted Owl flying
Spotted Owl flying
Spotted OwlNorthern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Northern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Spotted OwlNorthern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Northern spotted owls (Strix occidentalis caurina) are mostly non-migratory, long-lived birds whose populations have declined in mature forests of western North America.
Barred owlBarred owls (Strix varia) have expanded their geographic range from eastern to western North America. Their newly expanded range now completely overlaps that of the federally threatened northern spotted owl (S. occidentalis caurina).
Barred owls (Strix varia) have expanded their geographic range from eastern to western North America. Their newly expanded range now completely overlaps that of the federally threatened northern spotted owl (S. occidentalis caurina).
Up Close: LA Barred OwlThis Barred Owl was fearless in Baton Rouge, LA
This Barred Owl was fearless in Baton Rouge, LA
Barred Owl (Strix varia)Barred owl perched. Species identification tentative.
Barred owl perched. Species identification tentative.
- Publications
If you are unable to access a product or publication online, you can request a copy by sending an email with your contact information and the publication's citation to fresc_outreach@usgs.gov or call (541) 750-1030.
Filter Total Items: 32Range-wide sources of variation in reproductive rates of northern spotted owls
We conducted a range-wide investigation of the dynamics of site level reproductive rate of northern spotted owls using survey data from 11 study areas across the sub-species geographic range collected during 1993–2018. Our analytical approach accounted for imperfect detection of owl pairs and misclassification of successful reproduction (i.e., at least one young fledged) and contributed further inAuthorsJeremy T. Rockweit, Julianna M Jenkins, James E. Hines, James D. Nichols, Katie Dugger, Alan B. Franklin, Peter C. Carlson, William L. Kendall, Damon B. Lesmeister, Christopher McCafferty, Steven H. Ackers, L. Steven Andrews, Larissa Bailey, Jesse Burgher, Kenneth P. Burnham, Tara E. Chestnut, Mary M Conner, Raymond J. Davis, Krista E. Dilione, Eric D. Forsman, Elizabeth M. Glenn, Scott A. Gremel, Keith A. Hamm, Dale R. Herter, J. Mark Higley, Rob B. Horn, David W Lamphear, Trent L. McDonald, Janice A Reid, Carl J. Schwarz, David C. Simon, Stan G Sovern, James K. Swingle, David Wiens, Heather Wise, Charles B. YackulicAnticoagulant rodenticides in Strix owls indicate widespread exposure in west coast forests
Exposure of nontarget wildlife to anticoagulant rodenticides (AR) is a global conservation concern typically centered around urban or agricultural areas. Recently, however, the illegal use of ARs in remote forests of California, USA, has exposed sensitive predators, including the federally threatened northern spotted owl (Strix occidentalis caurina). We used congeneric barred owls (S. varia) as aAuthorsDavid Wiens, Krista E. Dilione, Collin A. Eagles-Smith, Garth Herring, Damon B. Lesmeister, Mourad W. Gabriel, Greta Wengert, David C. SimonEffects of experimental removal of Barred Owls on population Demography of Northern Spotted Owls in Washington and Oregon—2018 Progress Report
Populations of Northern Spotted Owls (Strix occidentalis caurina; herineafter referred to as Spotted Owl) have declined throughout the subspecies’ geographic range. Evidence indicates that competition with invading Barred Owls (S. varia) has contributed significantly to those declines. A pilot study in California showed that removal of Barred Owls coupled with conservation of suitable habitat condAuthorsJ. David Wiens, Katie M. Dugger, Damon B. Lesmeister, Krista E. Dilione, David C. SimonGeographic variation in natal dispersal of Northern Spotted Owls over 28 years
The most recent comprehensive estimates of Northern Spotted Owl (Strix occidentalis caurina) natal dispersal distances were reported in 2002. Since then, Northern Spotted Owl populations have experienced substantial demographic changes, with potential attendant changes in natal dispersal distances, including temporal or geographic trends. We analyzed the natal dispersal of Northern Spotted Owls duAuthorsJeff Hollenbeck, Susan M. Haig, Eric D. Forsman, David WiensThree-dimensional partitioning of resources by congeneric forest predators with recent sympatry
Coexistence of ecologically similar species can be maintained by partitioning along one or more niche axes. Three-dimensional structural complexity is central to facilitating resource partitioning between many forest species, but is underrepresented in field-based studies. We examined resource selection by sympatric northern spotted owls (Strix occidentalis caurina), a threatened species under theAuthorsJulianna M Jenkins, Damon B. Lesmeister, David Wiens, Jonathan T Kane, Van R. Kane, Jake V VerschuylBarred owl research needs and prioritization in California
Barred owls (Strix varia) have reached high densities within the range of the northern spotted owl (S. occidentalis caurina) and are rapidly increasing in number within the range of the California spotted owl (S. o. occidentalis). Encroaching populations of barred owls pose a significant competitive threat to the viability of both spotted owl subspecies in California. In response, the Director ofAuthorsZach Peery, David Wiens, Robin Bown, Peter C. Carlson, Katie Dugger, Jack Dumbacher, Alan B. Franklin, Keith A. Hamm, Mark Higley, John J. KeaneIsolation by distance versus landscape resistance: Understanding dominant patterns of genetic structure in Northern Spotted Owls (Strix occidentalis caurina)
Landscape genetics investigations examine how the availability and configuration of habitat influence genetic structure of plants and animals. We used landscape genetics to evaluate the role that forest connectivity plays in determining genetic structure of the federally-threatened Northern Spotted Owl (Strix occidentalis caurina) using genotypes of 339 Northern Spotted Owls obtained for 10 microsAuthorsMark P. Miller, Raymond J. Davis, Eric D. Forsman, Thomas D. Mullins, Susan M. HaigVariation in inbreeding rates across the range of Northern Spotted Owls (Strix occidentalis caurina): Insights from over 30 years of monitoring data
Inbreeding has been difficult to quantify in wild populations because of incomplete parentage information. We applied and extended a recently developed framework for addressing this problem to infer inbreeding rates in Northern Spotted Owls (Strix occidentalis caurina) across the Pacific Northwest, USA. Using pedigrees from 14,187 Northern Spotted Owls, we inferred inbreeding rates for 14 types ofAuthorsMark P. Miller, Susan M. Haig, Eric D. Forsman, Robert G. Anthony, Lowell Diller, Katie M. Dugger, Alan B. Franklin, Tracy L. Fleming, Scott Gremel, Damon B. Lesmeister, Mark Higley, Dale R. Herter, Stan G SovernEffects of experimental removal of Barred Owls on population demography of Northern Spotted Owls in Washington and Oregon—2017 progress report
Populations of Northern Spotted Owls (Strix occidentalis caurina; hereinafter referred to as Spotted Owl) are declining throughout this subspecies’ geographic range. Evidence indicates that competition with invading populations of Barred Owls (S. varia) has contributed significantly to those declines. A pilot study in California showed that localized removal of Barred Owls coupled with conservatioAuthorsJ. David Wiens, Katie M. Dugger, Damon B. Lesmeister, Krista E. Dilione, David C. SimonGenetic differentiation and inferred dynamics of a hybrid zone between Northern Spotted Owls (Strix occidentalis caurina) and California Spotted Owls (S. o. occidentalis) in northern California
Genetic differentiation among Spotted Owl (Strix occidentalis) subspecies has been established in prior studies. These investigations also provided evidence for introgression and hybridization among taxa but were limited by a lack of samples from geographic regions where subspecies came into close contact. We analyzed new sets of samples from Northern Spotted Owls (NSO: S. o. caurina) and CalifornAuthorsMark P. Miller, Thomas D. Mullins, Eric D. Forsman, Susan M. HaigIntegrating count and detection–nondetection data to model population dynamics
There is increasing need for methods that integrate multiple data types into a single analytical framework as the spatial and temporal scale of ecological research expands. Current work on this topic primarily focuses on combining capture–recapture data from marked individuals with other data types into integrated population models. Yet, studies of species distributions and trends often rely on daAuthorsElise F. Zipkin, Sam Rossman, Charles B. Yackulic, David Wiens, James T. Thorson, Raymond J. Davis, Evan H. Campbell GrantEffects of experimental removal of barred owls on population demography of northern spotted owls in Washington and Oregon—2016 progress report
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 tAuthorsJ. David Wiens, Katie M. Dugger, Krista E. Lewicki, David C. Simon - News
News Releases and plain language summaries of some of our products.
- Partners
These are our partners.