Breeding Experience and not Age Modulates the Song Development of Pied Flycatchers (Ficedula hypoleuca)

Abstract

In songbirds, the development of the species-specific adult song involves a learning process that varies in extension. In species that incorporate new song elements throughout life (open-ended learners), variation in male song composition could be the result of either age or breeding experience. Using data from 16 yr of fieldwork on pied flycatchers (Ficedula hypoleuca), we aimed to disclose the individual contribution of these two factors on the species song characteristics, as well as their relation with morphology and plumage color changes. Finally, we explored whether any of the song or physical features could predict the probability of males returning to the breeding site. We found that the song characteristics of the first-time breeders did not differ between age classes, except for the total number of syllables per song, which was higher in the 1-year-old than in the 2-year-old males. However, we found that song variables associated with complexity (song and sample versatilities and repertoire size), increased significantly from the first to the second breeding season. Males showed delayed plumage maturation, with 1-year-old males being browner than the 2-year-old males independently of their breeding experience. Morphology, however, was not affected by age or breeding experience. The probability that males returned to the breeding site was not associated with song or physical features. Considering that some song learning occurs during the breeding period and that some males may skip the first breeding season, selective pressures may have been established for song complexity to be an honest indicator of breeding experience rather than age.