Cooperative Fish and Wildlife Research Units Program: Missouri
Education, Research and Technical Assistance for Managing Our Natural Resources

Blakey, R.V., R.B. Siegel, E.B. Webb, C.P. Dillingham, R.L. Bauer, J.M. Johnson, and D.C. Kesler. 2019. Space use, forays and habitat selection in California Spotted Owls (Strix occidentalis occidentalis): new insights from high resolution GPS tracking. Forest Ecology and Management


Our current understanding of the relationship between imperiled species and forest management can benefit from global positioning system (GPS) technologies. Fauna of late-seral stage forests have historically been difficult to detect and track in rugged terrain, leading to challenges in movement characterization and conservation. We investigated movement of California Spotted Owls (Strix occidentalis occidentalis) using automated GPS loggers affixed to 15 owls in the northern Sierra Nevada, California. We used > 17,000 locations from individual owls to characterize summer home-range size, movement distances, roosting habitat selection, and foraging habitat selection at four spatio-temporal scales (landscape, home range, foray, nightly). Additionally, we assessed owl use of Protected Activity Centers (PACs), which are designated by the US Forest Service to protect nesting and roosting habitat. Our results corroborated some previous findings about habitat requirements of California Spotted Owls, while also revealing nuances in space use and habitat selection. Roosting and foraging owls selected for stands with high canopy cover and large trees at multiple spatio-temporal scales, with foraging owls showing strongest selection at the largest (landscape) scale investigated. Although owls selected for PACs while foraging and roosting, PACs protected less than a quarter of foraging space use (volume of use) and fewer than half of observed roosts. Home ranges of female owls were double the size of male home ranges, and distances travelled from the nest by females were 1.3 times greater than distances travelled by males, with non-breeding females travelling farthest and visiting up to eight PACs during a season. Foraying behavior of this sort has not been documented previously in Spotted Owls. Our findings support protection of later seral stage forest attributes for both roosting and foraging California Spotted Owls. Given the selection for later seral forest attributes, strongest evidence of foraging habitat selection at the landscape scale, relatively limited habitat protection afforded by PACs and the long distances travelled by owls, habitat connectivity across the landscape is important for owl conservation, and current protected areas may not be sufficient for this wide-ranging species.