Not for Parents Only: Begging Calls Allow Nest-Mate Discrimination in Juvenile Zebra Finches
Résumé
The benefits of recognition of family members may range from inbreeding avoidance to cooperative and coordinated behaviors within the family group. In birds, recognition of family members has almost exclusively been studied between parents and offspring or within cooperatively breeding societies. Yet, recognition of nest-mates could be of special importance in recently fledged birds of colonial species by helping in locating the nest, maintaining family group cohesion, or allowing detection of feeding opportunities by recognizing the begging calls nest-mates produced on the return of a parent. Here we study nest-mate discrimination based on begging calls in fledglings of domesticated zebra finches (Taeniopygia guttata), a gregarious songbird living in loose colonies in which juveniles may gather in crèches and are fed by parents up to 20 d after fledging. Using playback tests, we show that fledglings called more and spent more time near the loudspeaker in response to the begging calls of their nest-mates than to the calls of other familiar individuals. Because each fledgling was exposed to the repeated association of the begging calls of its nest-mates and the subsequent feeding of its parents, this preferential response to the nest-mates' calls could be a conditioned response to the food reward. Whereas fledglings answered more to male fledgling calls than to female fledgling calls, response to playback was influenced neither by the sex of the subject nor by its brood size. Discriminant function analysis based on acoustic parameters showed that begging calls carried an individual signature as well as a brood signature which might account for such nest-mate discrimination. Begging signals are major study systems of the evolution of communication in the face of conflicts of interest between signalers and receivers. Our results suggest that eavesdropping and communication networks may be other informative frameworks to understand the design of offspring solicitation signals.