It’s tough to be heard in the city: Adaptations of bird song in urban environments

Modern, high-density urban environments are an evolutionarily recent habitat in which urban features such as uniform grey cement surroundings, tall buildings with reflective surfaces, and loud low frequency ambient noise pose a variety of novel selection pressures to animals that live in this environment. The ambient noise environment can affect the perception of acoustic mating signals and mask signal content. Because acoustic communication is a critical component of both male-male competition and female mate choice in many taxa including anurans, crickets, and birds, the effects of urban ambient noise on signal transmission might have significant consequences for mate choice and resource defense across a diversity of taxa. A plethora of studies have found that birds and amphibians in urban environments produce vocalizations with higher minimum frequencies compared to the vocalizations of more rural populations. This study investigates the songs and behaviors of white-crowned sparrows in and around San Francisco to better understand the mechanisms and consequences of song evolution in an urban environment.