Why hoard? The economics of food storing in tits, Parus spp.

We present two models of food storage by small birds such as tits (Parus spp.): a simple, energy-maximizing model and a more complex dynamic programming model. The results show that hoarding is advantageous when (1) the metabolic costs of carrying reserves are high, (2) food supply is variable, (3) the mean rate of intake is low, and (4) overnight expenditure of energy is high. The dynamic programming model predicts daily routines of storing and retrieval as well as changes in body mass. The predicted routine (storage in the early part of the day, retrieval near dusk) has been observed in some species that store food. We predict differences in the pattern of change of body mass through the day between storers and nonstorers, but data to test this prediction are not yet available. [Behav Ecol 1990;1:12-23]