Sexy Songs

Few people have given as much thought to how bird songs change over time as Heather Williams, the college’s William Dwight Whitney Professor of Biology. In a recent paper in the scientific journal Animal Behaviour, she and her co-authors examine how and why Savannah sparrow songs have evolved over a period of 30 years.

As is the case for many songbirds, only the male Savannah sparrow sings. They reach out vocally to attract a female mate, adapting parts of their songs to compete with other males and better communicate their desirability.

Working on Kent Island in the Bay of Fundy, Williams and her team recorded the songs of specific male birds tagged by researchers with colored leg bands. They also tracked the number of offspring for each bird.

Williams found that some parts of the sparrow song changed little, if at all. Other segments varied rapidly over time. Still other sections changed systematically across generations. In these sections, where cultural evolution was evident, the “vocal virtuosos” learned to sing several clicks in rapid succession. These “sexier” songs attracted more females, and, as a result, these males had the most offspring.

Williams teaches courses on animal behavior, animal communication and neuroscience and is interested in the learning and organization of birds’ songs and the circuitry of their brains. Listen to the different segments of the Savannah sparrow’s song and watch a clip of the sparrow below.