Nest defense and central place foraging: A model and experiment

Summary

A graphical model presented here indicates that a nest-defending forager should stay closer to its nest, forage for shorter times per patch, and deliver smaller loads than predicated for delivery rate maximization. The effect is more pronounced farther from the nest, so that if nest defense is especially important, the predator should leave far patches sooner than near ones, and deliver smaller loads from farther away. Moreover, if the attack rate at the nest is increased, the defending forager should move closer and deliver smaller prey.

Experimental attacks with stuffed specimens at Gila woodpecker (Melanerpes uropygialis) nests produced the predicted changes in the foraging behavior of males, but not of females.

Mated pairs may work as a team to pursue simultaneously two conflicting goals—food delivery and nest protection—both of which affect the survivorship of the young. Sexual dimorphism in monogamous species may result in part from specialization in these roles.