African birds called pied babblers turn out to have their own version of goofy baby-feeding noises—think "Mmm nummy nummy aaaapricots." What's more, the birds actually teach their chicks that the sounds mean food, says Nichola Raihani of the University of Cambridge in England.

To test whether the babblers were actively teaching, Raihani and collaborator Amanda Ridley of the University of Cape Town in South Africa examined whether the bird parent modified its behavior around the chicks in a way that promoted learning but inconvenienced or offered no benefit to the adult.

The researchers watched clusters of the Turdoides bicolor babblers, medium-sized black-and-white birds, cooperating to raise chicks. Adults feeding the chicks often fluttered their wings and made a purring sound heard only when chicks were present. The researchers found no benefit of the behavior to the adult. In fact, the babblers that purred and fluttered a lot were the most likely to lose weight by the time chicks fledged.

To study effects on the chicks, the researchers broadcast extra purrs during mealtimes near some of the very young broods, when adults were just starting the behavior sporadically. For other broods, the researchers broadcast purrs when no food was in sight. After 2 days, the chicks in the mealtime-broadcast nests were ahead of their age-group in readily begging at the sound of a purr. The wrong-time-broadcast chicks had little to no response.

The youngsters are learning, Raihani and Ridley conclude in the January Animal Behaviour.

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