Ecology and behavior of Steller's jays (Cyanocitta stelleri) in human-influenced landscapes

Synanthropic species, which benefit from ecological associations with humans, have increased nearly globally as a result of the expansion of human activities and concomitant increases in the availability of anthropogenic foods. Predictable anthropogenic food subsidies are considered responsible for increases in populations of many overabundant synanthropes that impact a host of sensitive species. Understanding how patterns of anthropogenic subsidies on the landscape affect the behavior, distribution, and demography of synanthropic species is considered essential for reducing their effects on ecological systems and is an emerging conservation concern. Steller's jays (Cyanocitta stelleri) are synanthropic nest predators that have become widely and abundantly distributed throughout their range in western North America and have gained attention in the Pacific Northwest due to their association as nest predators of marbled murrelets (Brachyramphus marmoratus) and other nesting songbirds. Populations of Steller's jays have increased dramatically in parks containing remnant populations of murrelets, presumably a response to the availability of anthropogenic subsidies in these areas, with important consequences at the individual and population levels. My dissertation investigates the role of human activity -- with a particular emphasis on human food subsidies -- on the foraging ecology, behavior, and demography of Steller's jays. Using stable isotopes to analyze diet, radio-telemetry to characterize breeding and non-breeding season habitat use, and estimates of abundance, fitness and survival, I examined jays at multiple scales in California. Each chapter of this dissertation is written and formatted as a manuscript for publication in a scholarly journal. Chapter 1 (published in Ecosphere) characterized space use and dietary patterns in jays and showed that anthropogenic foods were an important component of jay diets in protected areas and that jays exhibited a functional response to anthropogenic foods as park visitation increased. Chapter 2 (published in Oecologia) integrated physiological, behavioral, and demographic information to test resource matching hypotheses in jays, and showed that jays were under-matched to prevalent resource subsidies despite high densities and behaviors expected to lead to resource matching. Results from this chapter also indicate that local food subsidies within protected areas can result in source habitats for synanthropes, potentially impacting sensitive species over broader spatial scales. Finally, Chapter 3 (prepared for submission to the Journal of Applied Ecology) investigated the strategies that jays -- with an emphasis on juveniles -- use to survive when abundant food resources in heavily visited areas of parks are only seasonally available. Results suggest that juveniles subsidized as fledglings by seasonally available anthropogenic resources in parks disperse to exploit more seasonally stable food resources in urbanized areas during the post-fledging period, a behavior that appears to promote high juvenile survival. High natal fidelity in jays indicates that year-round subsidies in urbanized landscapes surrounding parks can bolster populations of synanthropic species in protected areas, potentially threatening sensitive species. Overall, my research demonstrates the remarkable influence of anthropogenic food subsidies on the foraging ecology and behavior of Steller's jays, with associated effects at the individual and population levels, and provides management recommendations for jays and synanthropic species in general.