Song repertoire is not affected by stress in an adult male songbird, the Whitethroat Sylvia communis

Abstract

Summary It is believed that bird song has evolved as a reliable signal of quality of displaying individuals. Recent research has focused on costs of development of complex song. In the present paper we test if the acquired repertoire size is costly to maintain. We compared changes in song structure in male Whitethroats (Sylvia communis) after 48 h exposure to a stressor (5% body mass weight attached to the tail feathers) vs. changes observed within the same time interval in the control group. The strophe length was marginally significantly shorter in the handicapped males comparing to controls. However, the repertoire size (i.e., a measure of diversity of different song elements) remained intact in both groups. We concluded that the song repertoire in Whitethroats is a static secondary sexual trait. A review of literature has revealed no convincing examples of decreasing repertoire size in adult male songbirds. Further research is needed to improve our understanding of evolutionary and proximate mechanisms maintaining the stability of song repertoires.