CENTRAL PLACE FORAGING IN STARLINGS (STURNUS-VULGARIS) .2. FOOD ALLOCATION TO CHICKS

Two models of the proximate control of short-term parental decisions were developed. The regulation model predicts food allocation assuming that the parent eats the amount of food necessary to compensate its expenditure and gives the excess to the chicks. The LRS model uses assumptions derived from maximization of lifetime reproductive success. The main assumptions are that: 1) current brood productivity is a positive, negatively accelerated function of rate of food provisioning to the nest, and 2) residual reproductive value of the parent is a positive, negatively accelerated function of rate of parental intake. Instantaneous control of food allocation is assumed to maximize the sum of current brood productivity plus residual reproductive value of the parent. The role of biparental food provisioning is discussed. Food allocation, measured in field experiments using artificial feeding stations, was sensitive to both harvest rate and brood size, as predicted by the LRS but not by the regulation model. The LRS model has acknowledged shortcomings: it uses rates of intake and provisioning without reference to consequent changes in state of brood and parent, it does not incorporate the finite time horizon imposed by the time of independence of the young and stochasticity is not considered. These shortcomings can be overcome using stochastic dynamic modelling techniques. -from Authors