Role of begging and sibling competition in foraging strategies of nestlings

We assume that parents use the signalling intensity of their young to determine how much food they bring to the nest, and that the pattern of food allocation is determined by the signalling intensity and by the intensity of other nonsignalling behaviours that are not perceived by the parents. We explore different ways in which signalling, nonsignalling behaviours and competitive asymmetries might interact to determine food allocation. In Model 0 only signalling affects food allocation. More competitive chicks beg less and obtain a greater share of the food than their smaller siblings. In Model 1, a linear combination of signalling and nonsignalling behaviours determines food allocation. When nonsignalling behaviours are the main determinant of food allocation, chicks do not signal and parents deliver a fixed amount of food. Larger chicks receive a greater share of this food. When both types of behaviour are equally weighted, the pattern of investment depends on competitive asymmetry. For low asymmetry levels, both chicks invest in signalling. For large asymmetries, the less competitive chick invests in signalling and the more competitive chick invests in nonsignalling behaviours. In Model 2, the product of signalling and nonsignalling intensities determines food allocation. Larger chicks invest more in signalling and less in nonsignalling behaviours. Larger chicks get more food than their siblings. Overall chicks waste more resources when signalling evolves. Hence, if natural selection could act on the mechanism of food distribution, we would expect signalling to play a minor role in the actual pattern of allocation of resources.