Diversity and plasticity in branch-side use by birds in mixed-species flocks: niche differentiation or competitive hierarchy

Abstract

ABSTRACT Two models of mechanisms have been proposed to account for resource partitioning between species with overlapping niches, i.e., niche differentiation and competitive hierarchy. I examined branch-side uses by color-marked individuals of eight canopy-foraging species (Long-tailed Tit Aegithalos caudatus, Marsh Tit Parus palustris, Great Tit P. major, Eurasian Nuthatch Sitta europaea, Japanese Pygmy Woodpecker Dendrocopos kizuki, Great-spotted Woodpecker D. major, White-backed Woodpecker D. leucotos and Grey-headed Woodpecker Picus canus) in mixed-species flocks on artificial feeding trees for three years. The three tit species and the Nuthatch used the upper sides of branches most frequently whereas the four woodpecker species used the lateral sides of the branches most frequently, as expected from the niche differentiation model. Among the three tit species and among the four woodpecker species, small-subordinate species foraged on a wider range of branches than large-dominant species, as expected...