Effects of begging on growth rates of nestling chicks

We investigated whether an increase in begging levels delays growth of chic ks. 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 be gging. Squabs stopped responding to the treatment after 10 days and, at tha t time, there was no effect of induced begging on their body mass. In exper iment 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 be gging 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.