Risk indifference in white-eared hummingbirds (Hylocharis leucotis) confronting multiple foraging options

Abstract

Variations in the quality or quantity of a food source determines if an animal takes the risk of spending energy searching for or eating it. Hummingbirds have been traditionally catalogued as risk-averse foragers. However, the inclusion of more than 2 options in a foraging set for risk-sensitive experiments has resulted in the observation that some hummingbird species preferred intermediate risk even if they had been risk-averse in a traditional binary risk experiment. These contrasting results suggest an effect of having multiple foraging options that had been ignored due to the design of previous risk experiments. Here, we studied the influence of varying reward volume (Experiment 1) or sugar concentration (Experiment 2) on choice behavior of white-eared hummingbirds, Hylocharis leucotis, by recording their visits to feed from a sucrose solution located in 4 artificial floral arrays associated with constant, low, medium, and high variance. In both experiments, each of the vertical arrays was evaluated in a training stage and a test stage. The birds visited all the arrays without discriminating among them, and thus were indifferent to variations in the volume or sugar concentration of reward. Thus, there was no influence of variance of nectar volume and sugar concentration on the choice behavior of the birds, ruling out the possibility that white-eared hummingbirds are risk sensitive under these conditions of 4 foraging alternatives.