Urbanization drives changes in avian communities, which are reflected in the song of a vocal mimic

Urban landscapes present problems for wildlife including highly modified habitat, anthropogenic noise pollution, and competition for suitable habitat. These novel selection pressures can filter species present in urban habitats or result in changes to behavior. Recent studies show that some bird species sing differently (louder, higher pitch, faster) in noisier, urban areas compared to quieter, more rural areas, and that anthropogenic noise alone can exclude species. I investigated how the level of urbanization affects 1) bird species composition, and 2) the assemblage of species that a songbird mimics from the local bird community. I studied gray catbirds, Dumetella carolinensis, across an urban gradient (Washington DC to western Virginia, United States) and predicted that catbirds in urban habitats would mimic fewer species or simply mimic more urban-adapted species. Results showed that avian community composition differed along the urban gradient and was best predicted by impervious surface and noise level. The species composition of catbird mimicry was predicted by site soundscape, indicating catbird mimicry reflects the local avian community. Since urbanization level was found to significantly predict avian community composition, these findings support the hypothesis that urbanization impacts catbird song by influencing the community of sounds available for catbirds to mimic. Catbirds living in habitats of varying levels of urbanization have significantly different songs from catbirds in other habitats, due to their surrounding bird communities differing. Because song plays a role in reproductive success through mate attraction and territorial defense, these song differences may have implications for catbirds’ ability to persist and thrive in urban areas