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

Rindy C. Anderson, William A. Searcy, Melissa Hughes, Stephen Nowicki

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


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

Original languageEnglish (US)
Pages (from-to)1443-1448
Number of pages6
JournalAnimal Behaviour
Issue number6
StatePublished - Jun 2012


  • Aggressive signalling
  • Melospiza melodia
  • Receiver-dependent cost
  • Signal cost
  • Soft song
  • Song sparrow

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Ecology, Evolution, Behavior and Systematics


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