Comparative Feeding Ecology of Twenty-Two Tropical Piscivores

Abstract

Twenty-two fish-eating predators on a Peruvian lake show differ- ences in hunting technique, habitat use, prey sizes, and prey species. The swimming predators take mostly different prey species. Waders differ in their prey species and sizes, and in the habitats in which they hunt. Perchers and cruisers hunt from different heights and take prey of different sizes and species. Many of the same types of differences are evident between groups using different hunting techniques, although several species pairs have remarkably similar diets. RESUMEN. Veintidos depredadores de peces en un lago de Peru muestran di- ferencias en las tecnicas de pesca, uso del habitat, tamafio y especies de las presas. Los depredadores nadadores, atrapan mayormente diferentes especies de presas. Las aves zancudas difieren en las especies y tamafios de las presas asi como en los habitats en los cuales pescan. Aves que se posan para pescar (perchers) y otras que recorren mucha distancia en su busqueda por presas (cruisers) pescan desde diferentes alturas y atrapan presas de diferentes tamafios y especies. Son evidentes muchas diferencias del mismo tipo entre grupos que usan distintas tecnicas de pesca, aunque varios pares de especies tienen dietas remarcablemente similares. Most comparative studies of potentially competing species have considered only closely related species on the assumption that morphological differences between those more distant insure relatively great differences in resource use. Root (1967) suggested that functional rather than taxonomic relationships are more important and that all species using the same class of resources should be considered because very different species can use the same resources. In lowland Peru, oxbow lakes attract many fish-eating species that use a variety of hunting techniques. Some of these piscivores wade, some swim and pursue prey under water, some dive from flight, others dive from perches, and one skims the surface. Little information has been published on many of these species, and even those that are well known in some parts of their ranges are poorly known in South America. In this paper, I compare the feeding habits of twenty bird, one mammal, and one reptile species that I saw capture fish, and I analyze behavioral and ecological relationships within this portion of the fish-eating community.