Stable isotope (C,N,O, and H) study of a comprehensive set of feathers from two Setophaga citrina

Oxygen, hydrogen, carbon and nitrogen stable isotopes were measured on a comprehensive sampling of feathers from two spring Hooded Warblers (Setophaga citrina) in Texas to evaluate isotopic variability between feathers and during molt. Isotopic homogeneity within each bird was found across all four isotopic systems, supporting the hypothesis that molt in these neotropical migrants is fully completed on the breeding grounds. Moreover, this homogeneity suggests that the isotopic composition of a single feather is typically representative of the whole songbird. However, each bird also has outlier feathers, which could signify regrowth of lost feathers after prebasic molt.