The Great Gray Owl (Strix nebulosa) is a California Endangered Species, with an estimated population size of only 100-200 pairs in the state. It is the largest owl in North America and one of the largest owls in the world. It is also one of the most reclusive bird species, which provides challenges in studying its life history.
Great Gray Owls have a Holarctic distribution, inhabiting boreal forests from Scandinavia across Russia to northern Mongolia and China, and across Alaska and Canada down to the Rocky Mountains, Pacific Northwest, and the Sierra Nevada.
Most of the California population is found in the greater Yosemite area, although breeding records extend on the western slope of the Sierra Nevada from El Dorado County to the boundary of Fresno and Tulare Counties. North of Yosemite, there have been scattered records in El Dorado, Nevada, Sierra, Yuba, Butte, Plumas, and Modoc counties with a few historic records in the Klamath Mountains in northwestern California. In California, Great Gray Owls most commonly nest in dense forest stands adjacent to montane meadows, where they hunt for rodents, although IBP has recently documented nesting areas that are considered atypical for this species (see the two peer-reviewed publications below).
IBP is engaged in multiple research and conservation efforts to benefit Great Gray Owls in California, including a collaboration with the California Department of Fish and Wildlife to develop a comprehensive Conservation Strategy for the Great Gray Owl in California (see sidebar). We also have an active research program, facilitated by partnerships with multiple government agencies and private land owners, that aims to better understand the species’ distribution and abundance in the state, habitat needs for nesting and foraging, and response to wildfire.
For more information about IBP’s work to study and conserve Great Gray Owls in California, please contact Helen Loffland.
IBP recently partnered with the California Department of Fish and Wildlife (CDFW) and the broader California Partners in Flight community to develop A Conservation Strategy for Great Gray Owls in California. The Strategy collates information from the scientific literature and interviews with 23 experts, and provides over 50 conservation recommendations that we believe offer the best chance of preventing extirpation of this species in California and increasing the population.
The Strategy is intended for use by state and federal land managers, private land owners, non-governmental organizations, and the scientific community. While not a regulatory document, it provides conservation suggestions to protect the owl. Though the Strategy is still under review by CDFW, we provide Version 1.0 here in the interim so land managers and interested parties can begin to make use of it.
Siegel, R.B., P. Pyle, and H.L. Loffland. 2018. Molt sequences in an extralimital Great Gray Owl detected over two winters in northwestern California. Western Birds 49:62–73. PDF
Polasik, J.S., J.X. Wu, K. Roberts, and R.B. Siegel. 2016. Great Gray Owls nesting in atypical, low-elevation habitat in the Sierra Nevada, California. The Journal of Raptor Research 50:194-206. (For a copy of this publication, please contact Rodney Siegel.)
Wu, J.X., R.B. Siegel, H.L. Loffland, M.W. Tingley, S.L. Stock, K.N. Roberts, J.J. Keane, J.R. Medley, R. Bridgman, and C. Stermer. 2015. Diversity of nest sites and nesting habitats used by Great Gray Owls in California. The Journal of Wildlife Management 79:937-947. (For a copy of this publication, please contact Helen Loffland.)
Wu, J.X., H.L. Loffland, R.B. Siegel, C. Stermer. 2016. A Conservation Strategy for Great Gray Owls (Strix nebulosa) in California. Interim version 1.0. The Institute for Bird Populations and California Partners in Flight. Point Reyes Station, California. PDF
Siegel, R.B. 2006. Surveying for Great Gray Owl on the Carson and Bridgeport Ranger Districts of the Humboldt-Toiyabe National Forest during the 2006 breeding season. Report to U.S.D.A. Forest Service Pacific Southwest Region. The Institute for Bird Populations, Point Reyes Station, CA.
Siegel, R.B. 2002. Surveying Great Gray Owls at Sierra Nevada sites outside the greater Yosemite area: results from the 2002 field season. Report to Region 5 of the U.S.D.A. Forest Service. The Institute for Bird Populations, Point Reyes Station, CA.
Siegel, R.B. 2001. Surveying Great Gray Owls on southern Sierra Nevada forests: results from the 2001 field season. Report to U.S.D.A. Forest Service Pacific Southwest Region. The Institute for Bird Populations, Point Reyes Station, CA.