Niche segregation of Himalayan river birds

The Himalayan Mountains have more specialist river birds than anywhere on earth, but factors permitting their coexistence have not been evaluated. We examined potential ecological segregation of five sympatric insectivores based on diet, morphology, and foraging behavior during the breeding and nonbreeding seasons in central Nepal. Little Forktails (Enicurus scouleri) and Brown Dippers (Cinclus pallasii) were highly aquatic in habitat use and diet (89–96% of prey of aquatic origin), but took prey that differed in size and composition. Spotted Forktails (E. maculatus) foraged primarily along channel margins, and took more aquatic than terrestrial prey (59% vs. 40%). White-capped (Chaimorrornis leucocephalus) and Plumbeous (Rhyacornis fuliginosus) water redstarts took primarily terrestrial or aerial prey by gleaning marginal surfaces and flycatching over channels. Two species were similar morphologically (Little Forktail and Plumbeous Water Redstart), but had different diets. Our results illustrate clear ecological separation among this guild of co-occurring river birds on one or more niche dimensions that we suggest is mediated by the physical complexity of mountain, riverine habitats.