UCLA

As the world urbanizes, wildlife species will be forced to adapt to changed environments to survive. Despite the variety of development patterns and urban design of cities, species must overcome the loss of open space and transformation of natural vegetation to survive. I investigated spatiotemporal patterns of bird distribution to reveal ways urban wildlife communities assemble and persist. I first explored five decades of changes in nest sites relative to ornamental tree usage and urban land cover in a raptor community near Los Angeles. I showed that nest site re-use varied by species over time, and that nest substrate choice has shifted from largely native to strongly non-native. The amount of urban cover around most species’ nest sites has increased, but Cooper’s Hawk nest sites have become more urban than expected. I then expanded the study area to include the entire Los Angeles Basin, assembling occurrence data for more than 50 species from the 1990s to present. Using phylogenetically-informed models, I identified two ecological traits that were significantly associated with occurrence in urban areas then and now: the tendency to nest on artificial structures (positively), and the tendency to use natural cavities (negatively). Phylogenetic relatedness was uncorrelated with urban occurrence, suggesting that a variety of birds – not just those in a few families or genera –persist or reinvade as the landscape urbanizes. Finally, I expanded my analysis to the world’s hawks (Accipitridae), using community-science records from 62 cities. Modeling three urban occurrence indices with life history traits, I found each index negatively associated with body mass, and found positive associations with both nest substrate and habitat breath. Again, I found no evidence of phylogenetic signal in the models, which suggests that although urban hawks tend to be smaller-bodied generalists, multiple lineages may succeed in cities. All three analyses provide examples of the potential of community science data, including historical datasets, to reveal patterns that might not be apparent from single studies in particular geographical areas. They also illustrate the persistence of ecological traits associated with urbanization, even as natural communities vary around the world and change over time