Heterospecific exposure affects the development of secondary sexual traits in male zebra finches (Taeniopygia guttata).

In many animal species, social signals can affect the reproductive physiology and behaviour of conspecifics. In a few species that exhibit vocal learning, exposure to conspecific and sometimes heterospecific sounds can also influence their vocal development. Here we show that heterospecific exposure can affect the development of secondary sexual traits of male zebra finches (Taeniopygia guttata). In a first experiment, we trained young males with a passive playback of domesticated canary (Serinus canaria) song. Song playback enhanced the sexual development of the birds: they started to sing during the presentation of a video clip of a female earlier during development and exhibited secondary sexual plumage ornaments faster than males of the control group kept in silence. Two out of five birds exhibited clear evidence of imitation of canary song. In a second experiment, we raised young male finches with young male canaries in pairs until adulthood. Again, the live contact with a heterospecific companion affected the development of plumage ornaments in finches. We also observed some evidences of vocal convergence, both for calls and song. Moreover, young males of both species could recognize the call of their heterospecific companion when adults. These results suggest that heterospecific exposure can affect both the sexual and the vocal development of the zebra finch and can have long lasting effects. This article is part of a Special Issue entitled: insert SI title.