Non-native shrubs and calcium availability are important for birds breeding in urban forests

Abstract

Global increases in urbanization requires us to better understand how species are adapting to novel ecosystems in urbanized environments. We conducted a multi-year study to compare how five bird species with different life history strategies responded to local- and landscape-scale factors within forests in an urbanizing landscape. We modeled the responses of species to factors that have been shown to influence habitat selection for forest breeding birds including soil, vegetation, food quality and availability, and land cover. We found that, within an urbanized landscape, local-scale variables related to Ca prey availability and vegetation cover explained variation in territory density for the five bird species. Specifically, territory density for Carolina Wren (Thryothorus ludovicianus), Eastern Towhee (Pipilo erythrophthalmus) and Gray Catbird (Dumetella carolinensis) were positively related to non-native shrub cover and Carolina Chickadee (Poecile carolinensis), Eastern Towhee, and Wood Thrush territory density were positively related to calcium rich prey availability. These results suggest that species-specific responses to vegetation structure and nutrient composition are important factors for habitat selection of birds within urban forests.