Three decades of cultural evolution in Savannah sparrow songs

Cultural evolution can result in changes in the prevalence not only of different learned song types within bird populations but also of different segments within the song. Between 1980 and 2011, we examined changes within different segments of the single songs of male Savannah sparrows, Passerculus sandwichiensis, in an island population. Introductory notes did not change. The buzz segment showed similar stability; although a rare low-frequency variant appeared and then disappeared, the buzz segments from 1980 and 2011 were essentially identical. The middle segment, made up of discrete notes assembled into several types, was variable. However, the form of the middle segment did not affect fitness and may serve to denote individual identity. The terminal trill decreased steadily in frequency and duration over three decades. Longer trills were associated with lower reproductive success, suggesting that trill duration was under sexual selection. The notes sung between introductory notes w...