Three decades of cultural evolution in Savannah sparrow songs

► Cultural evolution of Savannah sparrow song was followed over three decades. ► Species-typical introductory notes and the buzz segment were stable. ► The variable middle segment was not associated with fitness and may denote individual identity. ► Trills and intercalated introductory notes changed systematically and were associated with fitness. ► Increasing variance may be an indicator of directional cultural selection.