Text.Knowledge of the natal origins of individual birds could provide valuable information for waterfowl conservation and harvest management programs. We used stable isotopes to differentiate birds from major western North America production areas, thereby providing a means of elucidating the natal origins of waterfowl. We used a multi-isotope approach (δ³⁴S, δ²H, δ¹³C, δ¹⁵N) to determine if ducks originating from different geographic areas had unambiguous multi-isotopic signatures. During 1999–2001 we took secondary feathers from prefledged mallard (Anas platyrhynchos) and northern pintail (A. acuta) ducklings from 52 sites in western North America (n = 284). Ducklings from Alaska, northern Canada (YT, NWT), the Prairies (AB, SK, MB, MT, ND, SD), and California could be distinguished based upon their feather isotope values. Geographic patterns in feather isotopes were related to natural gradients produced by biogeochemical cycles and anthropogenic factors such as agrochemical usage. Stable isotopes are naturally occurring markers that may be a useful tool in the effective management of waterfowl populations.