Foraging niche structure and coexistence in a highly diverse community of Amazonian antbirds (Thamnophilidae: Aves)

The high species richness of antbirds (Thamnophilidae) in Amazonian lowlands, where as many as 40 species may coexist at local scales, represents a major challenge for ecologists to explain patterns of coexistence and niche evolution. I studied the foraging ecology of a local community of antbirds in a 2-Km² area of lowland forest in SE Peru to examine how co-occurring antbird species differ in their use of foraging resources, and whether these differences result in niche partitioning at the community level. I also examined whether resource use similarity was related to phylogenetic similarity in this local assemblage. Forty-four species of antbirds were detected in the study plot in a four-year period, with 30 species categorized as the local assemblage of common resident breeders. Multivariate analysis of foraging parameters showed that segregation at two height layers in two types of forest was more important than foraging substrates and maneuvers in explaining the differences observed in foraging behavior. However, a null model analysis revealed that at the community level, antbirds exhibited high foraging niche overlap, with average observed overlap significantly larger than expected by chance, indicating that antbirds prefer, rather than avoid, resources used by other species. No general relationship exists between phylogenetic similarity and niche overlap. Closely related species consistently exhibit high values of niche overlap, but some distantly related species also exhibit high niche similarity. Taken together, these results suggest that foraging niche similarity is the predominant pattern among co-occurring antbirds, and that positive interactions might explain the stable coexistence of species that use similar resources and habitats at a local scale.Science, Faculty ofZoology, Department ofGraduat