SEXUAL SELECTION AND THE EVOLUTION OF SONG

Songs are complex acoustic signals produced mainly during the mating season. Such signals are found in many taxa but are most typical of birds, frogs, and insects. Darwin (38) noted that in these groups males are the predominant singers, and for this reason he attributed the evolution of song to sexual selection, that is, selection due to competition for mates. Darwin could muster no direct evidence that song or other display influences mating suc­ cess; only recently has such evidence begun to accumulate. Our fIrst goal here is to review and evaluate evidence that song influences mating success, via either female choice or male contests. Although convinced that sexual selection shapes display behavior, Darwin could not explain the evolution of a relationship between display and mating success. Fisher (50) first gave such an explanation in his discussion of female choice and male threat display. Our second goal is to review ideas and evidence on the evolution of relationships between song and female choice, and between song and success in male contests. We focus on the question of why listeners have evolved to respond to song in the contexts of female choice and male contest.