USDA Forest Service

Pacific Southwest Research Station
Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Research Topics Ecosystem Processes

Sierra Nevada Ecosystems

West Nile Virus in Spotted Owls, Great Gray Owls, and Northern Goshawks: Health Assessment, Antibody Levels and Genetics

The Research

photo of Great Grey OwlCalifornia Spotted Owls (Strix occidentalis ocidentalis) (CSO), Great Gray Owls (Strix nebulosa) (GGOW), and Northern Goshawks (Accipiter gentilis) are taxa of high conservation concern. While conservation concern has primarily focused on the effects of habitat management to date, other risk factors, such as invasive species and disease, have recently arisen and may significantly increase extinction risk for these species. For example, range expansion of the Barred Owl (Strix varia) may result in CSO population reductions through competition, predation, or hybridization. Similarly, the emergence of West Nile Virus (WNV) has the potential to result in significant population declines for both CSOs and GGOWs. WNV was first detected in North America in 1999 and reached southern California in 2003. Observations from captive and wild populations of raptors from eastern and mid-western North America suggest that mortality may be high in some species, including Strix owls and Accipiters, and that WNV may pose a risk to population viability. Annual sampling of exposure rates in demographic study areas coupled with estimates of demographic parameters from ongoing CSO studies will provide the basis for estimating adult survival rates, the most sensitive demographic parameter affecting population growth in species with "bet-hedging" life history strategies, pre- and post-WNV exposure. Given the highly polarized political, social, and biological debates focused on CSO status and the effects of habitat management it is critical to assess the emerging threat to the viability of the species from WNV. Without these data to inform future debates and assessments, the role of WNV in potential future population declines will be speculative and argumentative. An understanding of the disease dynamics of WNV in combination with previously studied risk factors such as habitat loss and invasive species will be a critical aspect in determining how future conservation efforts and resources should be allocated in management efforts.


blue arrrow To determine prevalence of West Nile Virus in CSOs, GGOWs, and NOGOs prior to WNV activity in 2004 to establish base line serology data (blood chemistry, hematology, hemoparasites).
blue arrrow To develop a collection of samples that will form the basis for longer-term work investigating the effects of West Nile Virus on population genetic structure and health parameters, genomic basis of disease susceptibility, population structure, genetic variability and historic demography of CSOs, GGOWs, and NOGOs.

photo of a map of the Sierra Nevada Ecoregion


Sierra Nevada Bioregion, California.

Lead Scientists/Collaborators

1) Keane, J.J.; 2) Ernest, H.B.; Hull, J.M.; 3) Tell, L.A.; 4) Reisen, W.

1) John J. Keane
USDA Forest Service, PSW Research Station
Sierra Nevada Research Center
2121 Second St., Suite A101
ph: 530-759-1704

2) Holly B. Ernest and Joshua M. Hull
Veterinary Genetics Laboratory, Wildlife and Ecology Unit
University of California, Davis.

3) Lisa A. Tell School of Veterinary Medicine Teaching Hospital Avian Service
University of California, Davis.

4) William Reisen
Davis Arbovirus Research Unit
University of California, Davis.

Last Modified: Aug 29, 2016 10:56:27 AM