Hydrogen stable isotope analysis of feathers is an important tool for estimating the natal or breeding latitudes of nearctic-neotropical migratory birds. This method is based on the latitudinal variation of hydrogen stable isotope ratios in precipitation in North America (iDp) and the inheritance of this variation in newly formed feathers (iDf). We hypothesized that the typically strong relationship between iDp and iDf would be decoupled in birds that forage in marine food webs because marine waters have relatively high iD values compared to iD values for local precipitation. Birds that forage on marine prey bases should also have feathers with high i34S values, since i34S values for marine sulfate are generally higher than i34S values in terrestrial systems. To examine this potential marine effect on feather stable isotope ratios, we measured iD and i34S in the feathers of nine different species of raptors from both inland and coastal locations across North America. Feathers from coastal bird-eating raptors had consistently higher iD and i34S values than feathers from inland birds. Birds that had high i34S values also deviated strongly from the typical relationship between iDp and iDf. We recommend measuring both sulfur and hydrogen stable isotope ratios in feathers when some members of a migrant population could potentially forage in marine habitats. We suggest using a practical cutoff of i34S >10‰ to remove marine-foraging birds from a migrant sample when using stable isotopes of hydrogen to estimate the latitudinal origins of migrants because high iDf values for marine-foraging birds could potentially distort estimates of origins.