Simplicity rules the roost: Exploring birdbrain parental investment heuristics

Parents raising multiple offspring must decide how to divide resources between them. Much empirical data on the parenting behaviour of particular species has been collected. Birds, in particular, have been shown to follow a number of provisioning rules. However, the adaptive significance of this variation in decision-making strategies has been largely unexplored. Here we present a simulation model of the western bluebird, Sialia mexicana, with which we explore the utility of various simple feeding heuristics. The simulated parents face the task of simultaneously raising several offspring who are of differing ages and thus have differing resource needs. We show that the success of simple rules of thumb varies with environmental parameters in a manner which (i) predicts experimental results in the biology literature, and (ii) can be explained using a notion of parental egalitarianism.