Divergent character displacement in the song of two allospecies: the Pied Flycatcher Ficedula hypoleuca, and the Collared Flycatcher Ficedula albicollis

Abstract

Songs of the three flycatcher forms, Ficedula hypoleuca hypoleuca, Ficedula albicollis albicollis and Ficedula albicollis semitorquata, were distinguishable from one another using a multivariate analysis. F. albicollis semitorquata, which has an intermediate song character, is considered to be a primary allopatric form while the nominate subspecies of albicollis is assumed to be dispersed into sympatry with F. h. hypoleuca. The differences in song between the nominate albicollis and F. hypoleuca are accentuated in their zone of sympatry and are mostly due to divergence in the albicollis song. The song is primarily an epigamic vocalization in the two species and conforms to the pattern characteristic of divergent character displacement associated with reproductive behaviour. Two alarm calls are quite similar in the two species and are the main vocalizations associated with territorial combat. Their interspecific territorial behaviour has apparently not been affected in areas of sympatry.