Evolution in action: Brown-headed Cowbirds (Molothrus ater) adapt songs to 50 years of Ohio urbanization

Technological advances in the last century have allowed humans to rapidly alter the landscape, resulting in a global loss of biodiversity. Of such alterations, is the conversion of rural land into urban space. In birds, urbanization has been found to impact song to facilitate improved auditory communication between conspecifics in areas with increased background noise. Given that birdsong is an important reproductive behavior, it is possible that urbanization promotes the evolution of birdsong through differences in fitness between individuals in urban acoustic environments. Here, we investigated if urbanization across Ohio impacts song characteristics of Brown-headed Cowbirds (Molothrus ater), a brood parasite associated with cropland and other altered habitats. To assess change in M. ater song over space and time, we compared syllable shape and syllable properties with metrics of urbanization. It was found that M. ater song differs significantly across geographic space and time, and is associated with changes in urbanization. Cowbird song of conspecifics in preferred habitat, such as cropland, demonstrates different syllable shape than conspecifics in urban space. This suggests that urbanization could facilitate change in M. ater song over time. These results provide additional insight into how anthropogenic habitat alteration facilitates cultural evolution in birds, and allows for increased understanding of how human behavior contributes to altered ecological interactions.