Threshold model of feeding territoriality and test with a hawaiian honeycreeper.

A model is proposed predicting that in nectarivorous birds territorial behavior will occur above a lower threshold of nectar productivity in a foraging area and disappear above an upper threshold. These thresholds are determined by the daily costs of living of territorial and of nonterritorial individuals and by the pressure of competing birds for the resource. Decline of efficiency of territorial exclusiveness is predicted as productivity increases from the lower to the upper threshold. Hawaiian honeycreepers (Vestiaria coccinea) supported the model.