The receiver-dependent cost of soft song: a signal of aggressive intent in songbirds

摘要: Social costs are one mechanism whereby reliability in signalling systems can be maintained. We measured the strength of aggressive response to territorial playback ask whether ‘soft song’, a strongly signal song sparrow, Melospiza melodia, is enforced by social cost form receiver's response. also asked this imposed all receivers, or differential found primarily exclusively among most subjects. first each male's on his territory, and then tested responses ‘warbled’ soft broadcast playbacks. While we substantial variation individual aggressiveness, nearly males responded more warbled songs. Thus provide evidence that imposes receiver retaliation, possible explanation for how signal's Questions about remain, notably why selection should favour low amplitude vocal signals aggression songbirds.