Seasonal Patterns in Hydrogen Isotopes of Claws from Breeding Wood-Warblers (Parulidae): Utility for Estimating Migratory Origins

Abstract

ABSTRACT. The global decline in many species of migratory birds has focused attention on the extent ofmigratory connectivity between breeding and wintering populations. Stable-hydrogen isotope (�D) analysisof feathers is a useful technique for measuring connectivity, but is constrained by features of molt locationand timing. Claws are metabolically inert, keratinous tissues that grow continuously and can be sampledat any point in the annual cycle, thus providing potentially useful clues about an individual's previousmovements. However, variation in the rate at which claws incorporate local �D values is not well described.We measured �D values in claws of two species of Neotropical-Nearctic migrant wood-warblers (GoldenwingedWarbler and Cerulean Warbler) breeding in eastern Ontario, Canada to investigate the rate of �Dchange through the breeding season and the utility of claw �D values for estimating migratory origins. �Dvalues of claw tips from 66 different individuals, each sampled once during the breeding season, showed