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2 May 2018 Song and aggressive signaling in Bachman's Sparrow
Sabah Ali, Rindy Anderson
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Male Bachman's Sparrows (Peucaea aestivalis) have large vocal repertoires containing many song types and multiple categories of songs and calls. We examined the territorial defense function of the vocal repertoire of male Bachman's Sparrows by quantifying singing behaviors and aggressiveness in response to a simulated territorial intrusion. We compared vocal and other behaviors between the intrusion and post-intrusion periods, compared more aggressive males (attackers) with less aggressive males (non-attackers), and tested for signals that predict attack. During intrusion, subjects switched among their song types at higher rates, however, song switching did not differ between more and less aggressive males. More aggressive males sang more low-amplitude “whisper songs.” In line with previous studies of aggressive signaling in songbirds, Bachman's Sparrows appear to use low-amplitude song to threaten rivals. The eavesdropping avoidance hypothesis predicts that low-amplitude songs should have acoustic traits besides amplitude to minimize signal propagation and transmission range. The whisper songs of Bachman's Sparrows are quieter versions of primary song types. Thus, Bachman's Sparrow may be a useful species for testing other predictions of the eavesdropping avoidance hypothesis, and for testing whether reduced amplitude is sufficient to reduce the costs of eavesdroppers.

© 2018 American Ornithological Society.
Sabah Ali and Rindy Anderson "Song and aggressive signaling in Bachman's Sparrow," The Auk 135(3), 521-533, (2 May 2018).
Received: 8 November 2017; Accepted: 20 February 2018; Published: 2 May 2018
bird song
low-amplitude song
male–male communication
vocal complexity
whisper song
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