SONG, SEXUAL SELECTION, STARVATION AND STRATEGIC HANDICAPS

Peaks in song output at twilight, particularly dawn, are typical of many birds. Recent attention has focused on the honesty of male advertisement, and on whether dawn is a particularly good time for females to assess male quality. In the present model a male divides his times between singing and feeding. If he sings more he is more likely to starve. A natural outcome is that song acts as a strategic handicap and as an honest signal of male quality. By using stochastic dynamic programming, diurnal variation in female assessment is shown to have a profound influence on male daily routines, but dawn is rarely the best time for assessment of quality. Females do not much enhance their probability of pairing with a high-quality male by varying responsiveness to song with time of day; constraints on female time budgets probably have more influence on the timing of male song than does optimization of quality discrimination. But females do greatly enhance their discriminatory efficiency by remembering past song output (song is then more concentrated at certain times, particularly morning, and males may even remain silent on alternate days). In general, the harder the task demanded of a male, the more efficient is the female rule in discriminating male quality. © 1993 Academic Press, Inc.