Effects of Cooper's hawk predation and presence on songbird survivorship, nesting success, and community structure

Abstract

The field of urban ecology seeks to incorporate humans into ecological studies, particularly within the built environment. This can include both the study of urban landscapes, as well as the study of ecology in urban landscapes, with the latter often helping inform the former, strengthening our understanding of these manipulated landscapes and systems. Human preferences drive many decisions on land use, with both local and large scales influencing the landscape, distribution of wildlife and, ultimately, the functioning of ecosystems. In these three studies in urban ecology, I first investigate one such driver of land use change by examining patterns of second home development in an amenity-rich landscape. Using a mixed-method approach combining spatial data and interview analyses, my interdisciplinary colleagues and I investigate both the structural and behavioral aspects of amenity migration in San Juan and Okanogan counties in Washington State. Results indicate that second- homeowners' desire for privacy and escape is reflected in patterns of spatial isolation among second homes, with second homes more likely to be next to undeveloped parcels and public land (Okanogan County) or shorelines (San Juan County). I then focus on one guild of avian predators- diurnal and nocturnal raptors- and examine whether land cover characteristics or prey abundance better explains their presence along Seattle's urban-to-wildland gradient, finding a strong relationship between specific land use patterns and the presence of these often habitat and dietary generalists throughout the gradient. Lastly, I provide a detailed investigation into the effects of one of these raptor species- the Cooper's Hawk (Accipiter cooperii)- on the songbird communities within which they live, finding a slight negative influence on the survivorship and nesting success of species they tend to prey upon, no significant influence on species they tend to not prey upon, and very limited influence on the overarching structure of the avian communities.