Geographic variation in the isotopic (δD, δ13C, δ15N, δ34S) composition of feathers and claws from lesser scaup and northern pintail: implications for studies of migratory connectivity

Abstract

Stable hydrogen isotope (δD) measurements of bird feathers can reveal approximate North American latitudes where feathers were grown by linking feather δD values to well-defined geographic patterns in δD values in growing-season precipitation. In waterfowl, this approach may require caution because wetlands are potentially “disconnected” from predictable isotopic patterns in precipitation waters. Stable carbon (δ13C), nitrogen (δ15N), and sulphur (δ34S) isotope values of avian tissues may show geographic structure but can be complicated by land use. We analyzed claws of wintering adult northern pintails (Anas acuta L., 1758) from California and Texas, and feathers and claws of lesser scaup ( Aythya affinis (Eyton, 1838)) ducklings from northwestern North America, to determine geographic variation in δD, δ13C, δ15N, and δ34S values. Wintering pintails from Texas and California were distinguished with claw δD and δ15N values. In scaup, feather δD values differed among biomes and were positively associated with latitude; geographic variation in other isotopes was less pronounced. The δD values in feathers and claws of individual scaup ducklings were correlated. A positive relationship between scaup feather δD values and δD values in growing-season precipitation was similar to results reported for songbirds. Thus, δD values in waterfowl feathers can provide new knowledge about natal origins and moulting sites.