The Function(s) of Bird Song

Male bird song may attract and stimulate females and may repelmales, but the evidence that song is essential for accomplishingthese "main functions" is not abundant. Correlations betweenmale song traits (such as repertoire size or singing rate) andcomponents of fitness reveal that important information, perhapsabout overall male quality, is available for listeners. To determinewhether birds use that information, however, will require researchersto manipulate song traits independently of male quality. Havingthen determined more rigorously the "current utility" of song,we will more clearly be able to infer how selection has shapedparticular song traits. We envision progress in understandingthe function(s) of bird song if investigators 1) thoroughlydescribe natural events, 2) use lucidly stated, multiple workinghypotheses, 3) realize the potential differences in song functionamong divergent taxonomic units, 4) transcend correlationalstudies by doing ingenious manipulative experiments, and 5)reason carefully when developing scenarios of evolutionary origin.