Effects of Urbanization on the Avian Community of Oak Woodlands

Continued human population growth leads to further expansion of high-density population centers and agricultural land necessary to sustain them. With this urban expansion comes a myriad of effects on both native habitat and wildlife. In birds, these effects can have a variety of negative impacts on behavior and physical health. Habitat degradation, largely through various forms of pollution, leads to impaired immune responses, increased stress levels, altered behavior, and much more. The wide range of effects impacting wild birds and their habitat can also alter the structure of local communities. Only species that can survive on or adapt to the resources and conditions of the urban landscape fare well, leading to a reduction in avian diversity, and the homogenization of urban avian communities. The city of Chicago, together with the range of land use types around it, makes up an urban-rural gradient, providing an opportunity to study the effects of urbanization. Across this gradient, during the summers of 2018 and 2019, point-count surveys of breeding birds in 28 oak woodland patches were performed to measure the effect of urbanization on the local bird community. Contrary to similar studies, no significant effect of urban development was found on either density or overall species richness of breeding birds. When grouped by guilds, significant impacts on species richness were found. While some results matched expected patterns (omnivore species richness peaks at high levels of development), many did not. Granivores and ground-foragers tend to respond positively to urbanization but showed no significant difference here. The focus of this study on oak woodlands may be responsible, as a single habitat type is far more consistent than the whole of an urban-rural matrix. Additionally, the urban birds typically found in cities across the world do not typically inhabit woodlands, freeing up resources for local natives