Reproductively Dependent Song Cyclicity in Mated Male Mockingbirds (Mimus polyglottos)

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Abstract
Mockingbird (Mimus polyglottos) song has been demonstrated to function in the species' perennial territoriality. Data reported here suggest that this species' diverse song may also function intersexually in reproduction. Observations on the amount of song produced by identified males throughout the breeding season revealed a pronounced cyclicity in the occurrence of song. Further, song cyclicity was systematically associated with the nature of the breeding activity in progress. In each of six mated males, the amount of song increased substantially while the male was nest building. The amount of song decreased significantly during incubation and during the care of offspring. This relationship held even when the cycle of breeding activities was disrupted through nest loss; males resumed singing immediately, although losses often occurred during periods of very little song. Analyses indicated that the nest-building song burst did not result from the activities involved in nest construction itself but often preceded the first observed instance of nest building. Increased song during nest building cannot be explained by excess amounts of unoccupied singing time available to males not engaged in the care of offspring. The overall pattern of results indicates that Mockingbird song may function in reproductive as well as in territorial contexts. Further, the cyclic relationship between song and breeding activities suggests that song may constitute a mechanism by which the reproductive state of the female is rapidly reset in preparation for subsequent broods.