The social context of song mimicry: Song-matching dialects in indigo buntings ( Passerina cyanea)

Abstract

First-year male indigo buntings ( Passerina cyanea) that match the song of an adult neighbour gain an advantage in acquiring a female, in nesting and in fledging young, when compared with first-year males that do not match a neighbour's song (Payne 1982). Four hypotheses of the mechanisms responsible for the mimics' success were tested in the field. Song matching among neighbours was not involved with recognition of local demes or with assortative mating; the population structure of song neighbourhoods is open and songs are not signals of kinship or community. Song matching was not directed towards females in sexual mimicry, and females rarely switched from an old mate to a younger one with the same song. Song mimicry was not directed towards the neighbouring male whose song was copied, as he was no less aggressive towards a song mimic than towards non-mimics. Song mimicry was associated with the timing of territorial establishment and of associated dispersal and residence in the first-year males. Four out of six predictions of a hypothesis of intraspecific competitive mimicry among male buntings were realized. The results best fit the hypothesis that a male that mimics the song of an older neighbour may deceive his territorial competitors, the other first-year males, in mistaken individual recognition.