Comparative Diets of Obligate Ant-Following Birds at a Site in Northern Bolivia

Abstract

Stomach contents of five syntopic, obligate army-ant-following birds (Gymnopithys salvini, Rhegmatorhina melanosticta, Myrmeciza fortis, Phlegopsis nigromaculata, and Dendrocincla merula) from a site in depto. Pando, Bolivia, were studied. The species studied are highly intra- and interspecifically aggressive and are similar in foraging behavior. Diet composition and prey size differed little among species and were in general unrelated to trophic morphological characters or dominance status. Stomachs of dominant species, however, had greater numbers of prey items than stomachs of subdominants; this was the major dietary difference discovered within this obligate ant-following assemblage. The opportunistic resource-use pattern of these species is similar to that of other groups of species, such as some carrion or fruit-eaters, or temperate-zone insectivores during resource flushes, that rely on temporally or spatially superabundant resources. It differs from predictions based on bill length or body size.