DIETS OF 4 SYMPATRIC AMAZONIAN WOODCREEPERS (DENDROCOLAPTIDAE)

Contents of 78 stomachs from four widespread and sympatric species of Amazonian woodcreepers (Dendrocolaptidae) were examined to assess the role of diet in resource partitioning. Orthopterans (25-35%) and beetles (10-32%) dominated the diets of all four species, despite large differences in foraging behavior. A higher proportion of spiders in the diet of Dendrocincla merula was associated with specialized ground-foraging at army ant swarms; however, specialization on dead leaves by Xiphorhynchus guttatus resulted in no significant dietary differences from the substrate generalist X. spixii. Overlap in diet was much greater than overlap in behavior for all species pairs, and the degree of diet specialization was unrelated to behavioral specialization. Taxonomic representation of prey in stomach contents differed significantly from field sampling of available prey in the three species tested, with orthopterans apparently selected by all species and beetles selected by D. fuliginosa. We suggest that behavioral differences may have evolved to reduce overt aggression (interference competition) but may not serve to reduce diffuse competition for food among syntopic species. Segregation in substrate use, however, may allow high diet overlap, suggesting a case of niche complementarity among these species.