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

Abstract

Stable isotope analysis of feathers may help track populations of migratory birds throughout their annual cycle. We use deuterium isotope ratios in feathers (δDf) 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 δDf values that reflect long-term average deuterium isotope ratios in precipitation (δDP) on the breeding grounds. Most greater coverts and crown feathers, however, have δDf values that are more enriched than predicted based on the δDP of their wintering distribution. We also found significant interannual variation in the δDf values of tail feathers, greater coverts and crown feathers. Interannual variation in δDf of winter-grown feathers may be explained by El Nino/La Nina conditions that influence rainfall and thus δDP; feathers were more depleted following an El Nino year (2005) than a La Nina year (2006). Gender had no effect on the δDf values of any feathers sampled. Age influenced the δDf values of crown feathers but not greater coverts. This study therefore confirms that δDf of summer-grown feathers can be used to identify breeding locations, but suggests that the ability to use δDf of winter-grown feathers to assign individuals to winter locations is limited by weak spatial gradients and temporal variation in δDP.