Morfología y forrajeo para buscar artrópodos por colibríes altoandinos

Morphology and arthropod foraging by high Andean hummingbirds

Abstract

Ecomorphological analyses in hummingbirds have focused on mutual evolutionary changes that have shaped bills and corollas, neglecting parallel factors in the evolution of hummingbird morphology and ecology. Here, I highlight the importance of arthropod foraging by hummingbirds in ecological and morphological studies. I examined hunting tactics, prey selection, morphological structures and certain aerodynamic parameters of hummingbirds of a high Andean forest near Bogotá, Colombia, as a first approach to characterizing hummingbird arthropod predation in high mountain environments. For the four most abundant species, I evaluated three complementary sources of data (behavior, morphology and diet) and contrasted my results with three hypotheses derived from a previous study in tropical wet forests. The first of these proposed that curve-billed hummingbirds cannot effectively catch aerial prey and that they glean prey from the substrate, but was not confirmed by my data; neither did I find evidence to support the hypothesis that hummingbirds with medium-length, straight bills prefer flies and wasps, whilst those with long, curved bills prefer spiders. The third hypothesis, that wing aspect ratios in flycatchers are higher than those in hover-gleaners, was corroborated in the present study. One explanation that would reconcile the differences between highland and lowland findings is that individual nectar foraging strategies, territorial vs. traplining (related to wing shape), are more important than curvature or length of the bill in determining arthropod foraging references. The high Andean hummingbird community as a whole consumes more aerial prey than do lowland birds. There exist clear differences in arthropod consumption among species and even between sexes of each species. Furthermore, these differences were significantly related to wing, bill and leg morphology, and aerodynamic indices calculated for such species. I suggest that foraging for arthropods places morphological constraints on the hummingbirds' corporal design and urge future studies to take this into account.