Urbanization mediates the effects of water quality and climate on a model aerial insectivorous bird

Aerial insectivorous birds have experienced alarming population declines in eastern North America. Meanwhile, urbanization continues to increase rapidly, with urban land use comprising 69.4 million acres, or 3.6% of total land area, in the contiguous United States. Multiple environmental changes are associated with urbanization, including alterations to local climate, changes in habitat structure, and potential shifts in both terrestrial and emergent aquatic flying insects on which aerial insectivorous birds rely. Here, we investigated the linkages between urbanization, water quality, and Tree Swallow (Tachycineta bicolor) reproductive success and body condition at seven river-riparian sites representing urban and protected land use in Columbus, Ohio over five consecutive years (2014-2018). Tree Swallows at urban and protected sites relied on emergent aquatic insects for 37.4 and 30.8% (SD = 28.4 and 24.1%) of their nutritional subsidies, respectively. Despite the loss of environmental ...