Interspecific cross-fostering of great tits (Parus major) by blue tits (Cyanistes caeruleus) affects inter- and intraspecific communication

Abstract

Summary Bird song is used to attract mates and deter rivals, and also functions as a species recognition cue. It is a flexible trait affected by learning, hence the choice of song tutors may affect an individuals’ singing. By interspecifically cross-fostering great tits (Parus major) to blue tits (Cyanistes caeruleus) in the wild, we have manipulated the species recognition of great tits, which in turn has influenced their song. In the present study, we presented breeding great tit and blue tit control males with playback of the aberrant song of cross-fostered great tit males and playback of the normal song of control great tit males. Blue tit males responded more to cross-fostered than control great tit song while great tit males showed the inverse response pattern. This shows that interspecific cross-fostering may affect both inter- and intraspecific communication. However, the response of males of both species towards the song of crossfostered great tit males was not of the same magnitude as the response towards ordinary blue tit song; thus, the real species identity is to some extent maintained in the aberrant song of cross-fostered males.