Effects of begging on growth rates of nestling chicks

We investigated whether an increase in begging levels delays growth of chicks. In experiment 1, we hand-reared nine pairs of ring dove squabs, divided into a control and a begging group. All squabs received similar amounts of food, but those in the begging group had to beg for a prolonged period in order to be fed, while squabs in the control group received food without begging. Squabs stopped responding to the treatment after 10 days and, at that time, there was no effect of induced begging on their body mass. In experiment 2, we hand-reared 27 pairs of magpie chicks for 3 days. The design of experiment 2 was similar to that of experiment 1. Daily food intake and begging affected growth rates. On average, chicks in the begging group grew 0.8 g/day less than control chicks, which represents a decrease of 8.15% in growth rate. Because growth is usually positively associated with expected fitness, this demonstrates that begging is a costly behavior, an assumption routinely made in models of begging behavior.