Morphology and isotopic ecology in a radiation of South American passerine birds, Cinclodes

I used stable isotopes to explore the evolution of ecological niches in Cinclodes ovenbirds. Carbon and nitrogen isotopes defined three conditions in isotopic space: reliance on marine resources, on terrestrial resources, or on island resources subsidized by marine organisms. Hydrogen and oxygen were tightly correlated, and were negatively correlated with the elevation at which specimens were collected. I measured the breadth of the isotopic niche via the area of the 95% confidence ellipses in C/N and O/H spaces. Phylogenetically independent contrasts showed that the evolution of niche breadth in C/N isotopic space was positively correlated with than in O/H space. Species that evolved broad elevational ranges seem to have evolved wide resource use as well. Broad isotopic niches were phylogenetically derived relative to narrow niches. Broad niches appear to have evolved twice in the genus, and concurrently with long halluces and relatively pointed wings.