Road mortality is a major anthropogenic source of raptor mortality. While barn owl (Tyto alba; BAOW) populations appear stable in California, BAOWs are the highest-reported raptor species in the California Roadkill Observation System (CROS). We investigated how different environmental variables—such as precipitation, moonlight illumination, and adjacent landcover—influence BAOW roadkill occurrence. We studied roadkill distribution through 15 years along I-5 in California, which contains diverse landscape types and dense reports of BAOW roadkill. After controlling for observer effort, BAOW roadkill observations have been decreasing in CROS over time (m = -0.24), potentially indicating population decline. We ran generalized linear models (GLM) with variable values extracted for each point, and performed model comparisons to pinpoint the best fit. The models significantly (p < 0.01) showed BAOW roadkill observations decreased the closer the distance to shrub, grassland, wetlands, and urban landcover, and increased closer to farmland. Observations increased with greater moonlight illumination and lower annual precipitation. These results are consistent with BAOW foraging habitat (farmland), but leads to questions about the relationship between BAOW roadkill and foraging/nesting habitat distribution. This research highlights the need to understand why BAOWs are susceptible to vehicle collisions in order to create improved BAOW roadkill mitigation strategies.

Selena Cao recently graduated from the UC Davis Wildlife, Fish and Conservation Biology program in the Class of 2025. She started working for the Road Ecology Center in 2023 and has worked on camera trapping projects on various CA highways, and assisted in studies on median barriers and noise/light effects. Throughout her time at Davis, she has also assisted in care of a captive-bred Amargosa Vole colony, bird and macroinvertebrate surveys, and formation of the Scientific Illustration Club at UC Davis. After graduation, she currently works at the U.S. Fish and Wildlife Service office in Lodi, CA.