Variation in deuterium (δD) signatures of Yellow Warbler Dendroica petechia feathers grown on breeding and wintering grounds

摘要

Stable isotope analysis of feathers may help track populations of migratory birds throughout their annual cycle. We use deuterium isotope ratios in feathers (δD_f) to confirm that Yellow Warblers Dendroica petechia go through both a prebasic molt on or near their breeding grounds and a prealternate molt on their wintering grounds, and evaluate whether δD analysis of different feather types can help assign birds to breeding and winter origins. We show that primary coverts and tail feathers have δD_f values that reflect long-term average deuterium isotope ratios in precipitation (δD_P) on the breeding grounds. Most greater coverts and crown feathers, however, have δD_f values that are more enriched than predicted based on the δD_P of their wintering distribution. We also found significant interannual variation in the δD_f values of tail feathers, greater coverts and crown feathers. Interannual variation in δD_f of winter-grown feathers may be explained by El Niño/La Niña conditions that influence rainfall and thus δD_P; feathers were more depleted following an El Niño year (2005) than a La Niña year (2006). Gender had no effect on the δD_f values of any feathers sampled. Age influenced the δD_f values of crown feathers but not greater coverts. This study therefore confirms that δD_f of summer-grown feathers can be used to identify breeding locations, but suggests that the ability to use δD_f of winter-grown feathers to assign individuals to winter locations is limited by weak spatial gradients and temporal variation in δD_P.