Urban habitats and noise impact avian communities and shape vocal mimicry in a songbird

Abstract

Urban landscapes present problems for wildlife including highly modified habitat, anthropogenic noise pollution, and competition for suitable habitat. These novel selection pressures filter species present in urban habitats or result in changes to behavior. Recent studies show that some bird species sing differently in noisier, urban areas compared to rural areas, and that anthropogenic noise alone can exclude species. We investigated how the level of urbanization affects (1) bird species composition detected acoustically, and (2) the assemblage of species that a songbird mimics from the local bird community. We studied gray catbirds, Dumetella carolinensis, across an urban gradient (Washington, DC to Virginia) and predicted catbirds in urban habitats would mimic fewer species or mimic more urban-adapted species. The results showed 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 and noise levels differing.