Experimental evidence for teaching in wild pied babblers

Giving calls to alert conspecifics to the presence of food is widespread among mammals and birds. Although the circumstances affecting the function of food-associated calls have been well studied, data on how receivers come to associate these calls with food are lacking. Specifically, the possibility that individuals may be actively taught to associate certain vocalizations with food delivery has not been addressed. In pied babblers, Turdoides bicolor, adults often give purr calls when feeding young and offspring subsequently associate these calls with food delivery. We investigated how offspring come to associate purr calls with food, specifically addressing the question of whether adults teach nestlings to respond to these calls. Adults use purr calls only in the presence of offspring and purr-calling does not seem to result in immediate, direct benefits to adults. Rather, the function of purr-calling seems to be to promote offspring learning: experimental playbacks show that nestlings learn to respond to purr calls and that purr calls must be reliably paired with food delivery for learning to occur. By giving purr calls during feeding visits at the nest, adults apparently actively condition nestlings to associate these calls with food. This represents a novel form of teaching among nonhuman animals.