Functional Responses of Birds of Prey: Biases Due to the Load-Size Effect in Central Place Foragers

Abstract

Functional responses of birds of prey have been estimated from analyses of prey delivered by a forager to sedentary consumers, usually mate or offspring located in a nest. Large items of prey captured by these single-prey loaders are more often carried to the nest and often consumed at capture sites than small ones. Therefore, analyses of prey delivered at the nest will bias any estimate of functional response by the forager, which is the response of interest in a consideration of effects on prey population dynamics. Some simple graphical models are presented to illustrate these biases