Publication Date

Fall 2023

Degree Type


Degree Name

Master of Science (MS)


Environmental Studies


Lynne Trulio; Rachel O'Malley; Philip Higgins


Grasslands are regularly altered for development, agriculture, and animal farming which leads to habitat destruction and fragmentation and, ultimately, a loss of wildlife species. Though degraded, grassland ecosystems – including native and non-native species - dominate the landscape in the region of the San Francisco Bay Area east of the Bay. The western burrowing owl (Athene cuncularia hypugaea) is a native grassland species of California. The breeding burrowing owl population in the San Francisco Bay Area is resident, but burrowing owls from other parts of the range migrate into the region for the winter. The breeding owl populations in the San Francisco Bay Area have mainly been extirpated, and those that remain are very small. Using an observational study of summer and winter burrowing owls, I characterized the distribution, abundance and habitat characteristics of both breeding and wintering owls in three East San Francisco Bay Counties, Alameda, Contra Costa, and western San Joaquin. Overall, I found that migrants and residents select for different burrow and landscape qualities and that dietary habits differ between seasons. The results of this study indicate that managers should manage habitat for both summer and winter owls, especially by promoting healthy California ground squirrel (Otospermophilus beecheyi), American badger (Taxidea taxus), and Orthoptera populations and managing vegetation height and densities to attract both resident and migratory owls.