Effect of noise on development of call discrimination by nestling tree swallows, Tachycineta bicolor

Anthropogenic noise is increasing in intensity and scope, raising concern over its effects on wildlife populations. Laboratory studies suggest that exposure to elevated noise can interfere with the development of a young animal's ability to process social signals and, ultimately, its ability to communicate as an adult. Whether such effects occur in nature is unknown, however. Here, we present the first field experiments examining whether elevated noise affects the development of the ability to discriminate the vocalizations of different conspecifics. We exposed nestling tree swallows to white noise during development, and then tested, in both quiet and noisy conditions, whether they could discriminate their parents' provisioning calls and their nestmates' begging calls from those of other individuals. We predicted that noise would interfere with discrimination, because previous work showed that it decreased nestling detection of adult calls, ostensibly an easier task. Instead, noise had no discernible effect on discrimination of parental and nestmate calls, even though it reduced overall responses to adult calls, as shown previously. While our results show no long-term disruptive effect of noise on development, they also show no adjustments to sustained noise that might help nestlings better cope with noisy conditions.