UC Davis

Pressures from climate change, habitat loss, and environmental contaminants are implicated in declines of avian species worldwide. Promoting species diversity in the agricultural landscape has become a widely supported way to contribute to biodiversity conservation and farm sustainability; however, uncertainty remains about how to best accomplish these goals across different spatial scales. Raptors play a key role in ecosystem balance and can provide valuable natural pest control in agricultural landscapes. Raptors are largely migratory with spatially disjunct breeding and wintering grounds, connected by vast migratory routes and stopover locations that include agricultural lands. This renders many raptor species vulnerable to habitat loss and secondary poisoning from agricultural practices throughout their annual cycle. Prioritizing effort towards species with a disproportionate impact on ecosystems that may be highly impacted by human activity can be an efficient way to maximize conservation impact. In Chapter 1, we used a reduced representation genomic approach to investigate the genetic diversity and population structure of Cooper’s Hawks (Accipiter cooperii) with a focus on Western North America. We analyzed genetic data at 2,415 SNP loci from 340 individuals sampled during breeding or migratory life history stages partitioned among three regions (British Columbia, western, and eastern North America). We observed low levels of differentiation which indicates that Cooper’s Hawks are a largely panmictic species and experience high levels of gene flow. In Chapter 2, we studied the movement ecology of American Barn Owls (Tyto furcata) in the Central Valley of California to understand how land cover influences home range size and hunting behavior. We calculated 95% autocorrelated kernel density estimations and found an average home range size of 6.35km2. We classified hunting locations based on turning angle and velocity and used a resource selection function model to investigate land cover types that were selected for hunting. Barn Owls had the strongest selection of roadside margins for hunting, followed by all other land cover types except barren/fallow, which did not have a statistically significant result for selection. In Chapter 3, we investigated sublethal anticoagulant rodenticide (AR) exposure in free-ranging Red-tailed Hawks (Buteo jamaicensis) and Barn Owls in agroecosystems of Northern California. We detected a 0.5% circulating AR exposure rate in Barn Owls, although documented little to no AR-use at our study sites. We detected a 15% AR exposure rate in wintering Red-tailed Hawks, with a 36% AR exposure rate reported in the first sampling year. Immature Red-tailed Hawks were exposed more frequently than adults, and all compounds detected from hawks were second generation ARs. Increasing our understanding of raptor ecology across scales and through all life-history stages is critical for species conservation, preventing carryover effects, and developing strategies to mitigate challenges associated with the Anthropocene.