What is the Function of Song Learning in Songbirds?

Abstract

In this paper we approach the question of the function of song learning in songbirds by addressing the more particular question of why a bird chooses the particular songs he does from among the many songs he hears during his song learning period. Our generalizations about song learning are derived from observations of a sedentary (nonmigratory) population of song sparrows (Melospiza melodia). We examine this question in the field, rather than in the laboratory, because we believe that the variables controlling song selection are social and ecological. We proceed from the hypothesis that song learning is an adaptive strategy, and attempt to identify the specific design features and overall function of this strategy in our particular study species. From our studies, we have identified several design features which, taken together, serve to maximize the number of songs the young bird will share with his neighbors, especially his near neighbors, in his first breeding season. Why should it be advantageous for the bird to have songs he shares with his neighbors? We suggest four possible, non-mutually exclusive advantages, and discuss the evidence in support of the fourth one. First, shared songs may be attractive to females. Second, shared songs may provide a mechanism by which two neighbors might effectively codefend their territories against other birds: each bird would effectively be mimicking the other while repelling prospective intruders. Third, shared songs may function as a “badge” of familiarity among territorial males; shared songs are a reliable signal of familiarity since they must be learned in the local neighborhood. Fourth, at least in song sparrows, shared songs appear to facilitate communication among neighboring birds. In particular, a bird uses the songs he shares with a neighbor to direct his song to that bird. We conclude by noting the paradox that songbirds have the ability to improvise new songs (demonstrated in lab experiments), yet in the field birds of most species faithfully copy the songs of their older neighbors. We suggest that song researchers need to ponder this paradox, and figure out why it is so important for a songbird to have the same songs as his neighbors.KeywordsBreeding SeasonSong TypeYoung BirdRepertoire SizeSong SparrowThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.