Ecological and life history traits predict urban tolerance in North American birds

Urbanization poses a drastic threat to biodiversity, but does not affect all species equally. As such, identifying the life history traits and ecological characteristics that distinguish species that tolerate urban areas from those that do not is a central goal in urban ecology. Additionally, understanding whether shared evolutionary history influences urban tolerance could shed light on its evolutionary origins and reveal the extent to which urban landscapes filter out entire taxonomic clades, homogenizing biodiversity. Here, we assessed the relationship between urban tolerance and eight different life history and ecological traits for 431 North American bird species. We found that birds with higher urban tolerance are longer-lived, smaller-bodied, and more likely to be sedentary or mixed migrants than birds with lower urban tolerance. Birds with higher urban tolerance also have broader environmental tolerance, based on breeding range size and estimates of range-wide variation in precipitation, consistent with their greater likelihood of being habitat generalists. We additionally detected a phylogenetic signal for urban tolerance, with several clades sharing similar urban tolerance measures. Our study identifies several mechanisms that likely underlie species differences in urban tolerance and demonstrates how urban areas can filter bird species based on their life history and ecological traits.