The effect of variability in the food supply on the daily singing routines of European robins: a test of a stochastic dynamic programming model.

A stochastic dynamic programming (SDP) model offers a general explanation of daily singing routines in birds, but remains almost untested empirically. I examined a central prediction of the SDP model, that a more variable food supply decreases the bird's song output at dawn, relative to its song output at dusk. I provided supplementary food to make the food supply more or less variable over 2-week periods in the territories of free-living European robins Erithacus rubecula. Robins sang relatively less at dawn than at dusk after weeks in which their supplementary food supply was variable, and more at dawn than at dusk after weeks in which their food supplementation was constant. These results provide strong support for the prediction of the SDP model. Copyright 1999 The Association for the Study of Animal Behaviour.