FORAGING ECOLOGY OF 7 SPECIES OF NEOTROPICAL IBISES (THRESKIORNITHIDAE) DURING THE DRY SEASON IN THE LLANOS OF VENEZUELA

We describe the relative abundance. foraging habitat, and feeding behavior of seven sympatric species of ibises (Threskiornithidae) in the Venezuelan llanos during the dry season of 1989. Scarlet (Eudocimus ruber), Glossy (Plegadis falcinellus), and Bare-faced (Phimosus infuscatus) ibises were the most common species. White (E. albus), Green (Mesembrinibis cayennensis), Sharp-tailed (Cercibis oxycerca), and Buff-necked (Theristicus caudatus) ibises together made up less than 8% of individuals surveyed. Multivariate analyses showed that differences in use of foraging habitat partitioned the foraging niche during the dry season, a time when little aquatic habitat is available to the birds. Foraging habitats used by the seven species were differentiated by decreasing distance to water, in the following order: Buff-necked (dry land), Sharp-tailed and Bare-faced (moist soil, occasionally in standing water), Green (water's edge), and Scarlet, While, and Glossy ibises (nearly always in standing water). Probing depth, prey size, and height of vegetation fur-ther partitioned the niche. Large differences in capture, probing, and stepping rates were found among all species. There were no differences in foraging behavior or in foraging habitat between congeneric White and Scarlet ibises. Considerable overlap in foraging habitat in space and time was seen among the three aquatic foragers (White, Scarlet, Glossy), and aggression and occasional food robbery occurred among these species. Scarlet Ibises were most aggressive and were most likely to attempt food robbery.