Natural and anthropogenic sounds reduce song performance: insights from two emberizid species

Anthropogenic sounds influence animal vocal behaviour, species distributions, and community assemblages. Natural sounds also have the potential to affect the behaviour and ecology of animals, but it is currently unknown if the effects of natural sounds match those of anthropogenic sounds. Here, we quantified and compared the effects of natural and anthropogenic sounds on avian song performance by calculating trade-off frontiers based on trill rate and bandwidth of 2 emberizid species. Chipping sparrows (Spizella passerina) and white-crowned sparrows (Zonotrichia luecophrys) were recorded in areas with and without anthropogenic sound and along a natural sounds gradient generated from ocean surf, respectively. We analysed individuals’ song performance relative to the trade-off frontier and found that both species vocalizing in environments with louder background sounds sang songs that were significantly further below the trade-off frontier than songs sung by birds in quiet settings. Chipp...