Male whitethroats, Sylvia communis, advertise their future contribution to parental care

Abstract

Summary In altricial species participation of males in parental care enhances reproductive success of females. How does a female select a mate who will allocate time and energy to parental effort? In the whitethroat Sylvia communis, a socially monogamous bird, parental performance of males might be predicted on the basis of elaborated song flights displayed in courtship. The correlation analysis revealed that males which advertised intensively needed less time to attract a female and also their parental performance was better compared to males that produced cheaper signals. In the subsequent experiment, we handicapped males by increasing their body mass by 5% with a weight attached to tail feathers. Males in the treatment group reduced the proportion of showy song flights significantly more than controls and their mating success was significantly lower. We conclude that song flights in whitethroats honestly signal male quality and that the signalling system depends on a dynamic handicap trait which responds to a relatively small change in the male.