Songbirds' Cries For Food First Sign Of Vocal Learning  Songbirds |
A new research in songbirds shows that vocal experimentation begins with their earliest vocalisations - food begging calls and perhaps for a more wily reason than previously believed.
"It may have started as cheating," said Fernando Nottebohm, head of the Laboratory of Animal Behavior at The Rockefeller University.
"By generating a diversity of calls, young birds may trick their parents into losing track of whom they last fed, in effect creating the impression of several individuals." In this scenario, the most agile vocal dissembler would get more than its fair share of food at the expense of its siblings.
Nottebohm and Wan-chun Liu, research assistant professor who made the original observations, are quick to say that the interpretation remains speculative for now, but if true, it would complicate the conventional wisdom that vocal learning evolved as an adjunct to reproductive behaviour.
In temperate climates, most often only male songbirds sing. The message conveyed by song is simple: I am a male robin, mature, single and ready to breed; females are welcome, males stay away.
Depending on the listener, song is a lure or a threat. By imitating the song of established seniors with whom they would have to compete, young breeders presumably gained an advantage in courtship and territorial defence.
The vocal imitation expressed by adults, however, is a complex behaviour requiring sophisticated underlying brain circuits, Nottebohm said.
How would birds with only innate, genetically foreordained vocal repertoires have evolved the ability? One part of a plausible explanation is that vocal learning emerged initially as a vehicle for creating variability in juveniles before territory and mate are an issue, according to Nottebohm.
Such a development would require a simpler beginning brain circuit, which could later become part of the complex brain architecture required for imitation.
The new research is compatible with the idea that vocal learning first emerged outside the context of reproductive pressures, said a Rockefeller release.
Liu found that while the food begging calls of young males vary considerably from moment to moment and between individuals, those of young females are very stereotyped and all alike.
These findings were published in PLoS ONE.
