Can hungry nestlings be trained to reduce their begging?

Nestling begging behavior is usually characterized by a behavioral response of increasing begging levels with an increase in nestling need or hunger. Recent evidence for the possible effect of learning on begging intensity raises the question of how learning can shape this response rule. In particular, it is not clear whether hungry nestlings can learn to reduce their begging when it is not successful or, rather, whether they must first acquire positive experiences with low begging levels in order to do so. To explore this question, we conducted 3 hand-feeding experiments with pairs of house sparrow (Passer domesticus) nestlings. In the first 2 experiments, the nestlings targeted to lower their begging were rewarded mainly or only for low begging postures. However, despite the high expected reward for low begging, these nestlings did not lower their begging. Controlled by their behavioral response function, hungry nestlings were "stuck" at high postures without being able to experience the potential success of low postures. In the third experiment, nestlings targeted to lower their begging levels were rewarded for any begging posture, ensuring that satiation would provide their initial "positive experience" with low begging postures. Begging postures were reduced by this treatment. In light of these results, we suggest that parents are unlikely to reduce offspring begging levels by simply ignoring them. However, they might be able to do so by attending to the begging as soon as possible, thereby allowing their offspring to explore low begging and learn that it is sufficiently effective.