Heterospecific song quality as social information for settlement decisions: an experimental approach in a wild bird
Assessing local habitat quality via social cues provided by con- or heterospecific individuals sharing the same needs is a widespread strategy of social information use for breeding habitat selection. However, gathering information about putative competitors may involve agonistic costs. The use of social cues reflecting local habitat quality acquired from a distance, such as acoustic cues, could therefore be favoured. Bird songs are conspicuous signals commonly assumed to reliably reflect producer quality, and thereby local site quality. Birds of different species have been shown to be attracted to breeding sites by heterospecific songs, but whether they can use fine heterospecific song features as information on producer (and by extension habitat) quality remains unknown. We used a playback experiment in a wild population of collared flycatchers (Ficedula albicollis), a species known to eavesdrop on dominant great tits (Parus major) presence and performance, to test whether flycatchers preferred to settle near broadcasts of a high quality great tit song (i.e. song with large repertoire size, long strophes, high song rate), a low quality great tit song or a chaffinch song (control). Among old females, aggressive ones preferred to settle near broadcasts of high quality tit song and avoided broadcasts of low quality tit song, while less aggressive females preferred to settle near broadcasts of low quality tit song. Male personality or age did not influence settlement decisions. Our results show that collared flycatcher females use great tit song quality features as information for settlement decisions, though differently depending on their own competitive ability and/or previous experience with great tit songs. Our study therefore further illustrates the complex condition-dependent use of heterospecific social information for breeding habitat selection.