The Function(s) of Bird Song

Abstract

Male bird song may attract and stimulate females and may repel males, but the evidence that song is essential for accomplishing these “main functions” is not abundant. Correlations between male song traits (such as repertoire size or singing rate) and components of fitness reveal that important information, perhaps about overall male quality, is available for listeners. To determine whether birds use that information, however, will require researchers to manipulate song traits independently of male quality. Having then determined more rigorously the “current utility” of song, we will more clearly be able to infer how selection has shaped particular song traits. We envision progress in understanding the function(s) of bird song if investigators 1) thoroughly describe natural events, 2) use lucidly stated, multiple working hypotheses, 3) realize the potential differences in song function among divergent taxonomic units, 4) transcend correlational studies by doing ingenious manipulative experiments, and 5) reason carefully when developing scenarios of evolutionary origin.