Center for Conservation Biology

Northern spotted owl research

Conservation endocrinology

Two owls huddled on a tree branch in daylight

Two Northern Spotted owls (Strix occidentalis caurina) huddled on a tree branch in daylight.Photo by Zachary Folk

The northern spotted owl, Strix occidentalis caurina, is the flagship threatened species of the Pacific Northwest. Federally listed under the Endangered Species Act in 1990, the northern spotted owl continues to decline at a rate of about 4% throughout its range. Despite the fact that the northern spotted owl is one of the best-studied wild vertebrate species in the world, the relative importance of the threats that it faces remain controversial.

Our Center developed measures to help assess the relative impacts of pressures such as barred owl invasion, habitat loss and anthropogenic disturbance in northern spotted owl. We developed non-invasive fecal hormone measures of physiological (glucocorticoids) and nutritional stress (thyroid hormones) and reproductive activity (sex steroids) in northern spotted owl. We applied these tools to document impacts of off-highway vehicle and road exposure on the NSO and to further improve survey techniques for northern spotted owl and barred owls.