LINKING BROODING AND WINTERING GROUNDS OF NEOTROPICAL MIGRANT SONGBIRDS USING STABLE HYDROGEN ISOTOPIC ANALYSIS OF FEATHERS

Recent studies have shown that stable hydrogen isotope ratios (delta D ) in the tissues of animals often correlate with delta D of local prec ipitation. Here we examined the relationship between delta D in feathe rs and growing season precipitation for neotropical migrant songbirds breeding over a continent-wide isotopic gradient. delta D values were determined on feathers of 140 individuals of 6 species of wild insecti vorous forest songbirds (Setophaga ruticilla, Empidonax minimus, Vermi vora peregrinus, Catharus ustulatus, Seiurus aurocapillus, Hylocichla mustelina) taken from 14 breeding locations across North America. The delta D of feathers was strongly correlated with the delta D of growin g season precipitation at breeding sites across North America. As feat her hydrogen is metabolically inert after growth, this relationship wa s then used to assess the breeding origins of wintering migrants. Deut erium values of feathers from 64 individuals representing 5 species of migrants (Helmitheros vermivorus, Wilsonia citrina Hylochichla mustel ina, Dumetella carolinensis. Seirus aurocapillus) at a wintering site in Guatemala were consistent with those predicted from the known breed ing ranges of these species. This study demonstrates hydrogen isotopes may become a powerful tool for linking breeding and wintering grounds of neotropical migrant songbirds, as well as other mi,oratory species moving between isotopically distinct regions.