Peter J. B. Slater

Abstract

Song in birds is largely a male preserve, although females may sing also, espe-

cially in the tropics where some species exhibit complex duets. Song has two main

functions: repelling rivals and attracting mates. Species with the most complex

songs, in which individuals may have hundreds or even thousands of different

phrases, appear to be those in which sexual selection leads females to choose

mates with more elaborate songs. Even where repertoires are large, they tend,

once learned, to be fixed, and little evidence exists for improvisation. Mimicry

probably evolved as an alternative means to generate variety in song. Any sim-

ilarity between birdsong and human music is by analogy, as vocal learning

evolved quite separately in the two cases. As there are around 4,000 species of

songbirds with a rich variety of vocal patterning, the occurrence of some with

features also found in our music does not necessarily imply a deep similarity

between the phenomena.

Birds are among the most vocal of animals and, given the rhythmicity,

tonality, and variety of the sounds they produce, it is not surprising that

many of these sounds have come to be labeled songs. Is this just by

analogy with our own music, or can some real and useful parallels be

drawn? In this chapter I start by reviewing how and why birds sing. I

discuss examples of song repertoires in rather more detail, as the won-

derful variety of some of these is perhaps what gives the closest link with

music. In addition, I devote some attention to choruses and duets, as

these phenomena are especially striking in this context. Finally, I make

a few comments on the comparison between birdsong and music and

whether it has anything useful to tell us.

The How and Why of Birdsong

Perhaps the first question to ask is why animals, like birds or humans,

should use sound to transmit messages.Animals communicating with each

other from a distance can use several different senses, but smell, sight, and

sound are the most usual. Each sense has its advantages and disadvan-

tages (Alcock 1989). Whereas many animals, including birds, display to

each other with visual signals, such signals are mainly of use in short-range

and private communication.They are of little use at night, or when objects

intervene between signaler and receiver. Olfactory signals are excellent

when persistence is required and, as with animals marking their territo-

ries, even operate when the signaler has moved on. Like sounds they can

be detected at long range and spread round obstacles. But their very per-

sistence raises a disadvantage in that it is difficult to change quickly from

one message to another: they are thus not well adapted for the rapid

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Birdsong Repertoires: Their Origins and Use

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