Barred Owls (Strix varia) continue to expand through the Pacific Northwest and into the Sierra Nevada, California, threatening native species. In this study, we conducted genetic-based dietary analyses using intestinal samples from invasive barred owls collected at the front end of their California expansion to better understand potential impacts on wildlife communities. Using a diverse panel of DNA amplifying primers and high-throughput-sequencing, we successfully screened the intestinal contents of 124 barred owls, detecting a broad diet of 78 unique prey types (48 vertebrates and 30 invertebrates). Commonly consumed taxa of note included Douglas squirrel (Tamiasciurus douglasii), Northern flying squirrels (Glaucomys sabrinus), Sierra and Pacific tree frogs (Pseudacris sierra and P. regilla), dusky footed woodrats (Neotoma fuscipes), and several game and domestic species. Barred owl prey consumption demonstrates the potential for exploitative competition with spotted owls (Strix occidentalis), but also potential competition with sensitive species including fishers (Pekania pennanti) and Northern goshawks (Accipiter gentilis). Diet composition varied across an elevation gradient, based on forest conditions, and between the Sierra Nevada and Klamath regions. Our findings indicate that barred owls – as generalist predators – will not serve as ecological replacements for spotted owls should they continue to increase in relative abundance.

I have spent roughly a decade working with spotted owls in varying capacities, and as a graduate student have shifted my focus to the ongoing threat of invasive barred owls. Through lethally collecting barred owls and utilizing genetic sampling, I hope to provide insight into their range expansion and potential community effects, particularly in the Sierra Nevada ecoregion. While completing my graduate research I have also been able to provide field support to other ongoing projects in Northern California, providing training and assistance in methods such as surveying for, capturing, and handling/tagging both spotted and barred owls.