Nutrient fluxes across ecosystem boundaries are thought to have pronounced effects on ecosystem dynamics, but these interactions can be difficult to confirm in complex systems. Islands are ideal for studying nutrient subsidies as they have finite boundaries. The arctic islands of Hudson Strait are severely nutrient limited, mostly undisturbed, and recovering from relatively recent glaciation. These islands support many species of seabird, including the Common Eider (Somateria mollissima), which can nest in large island colonies. Eiders forage on benthic invertebrates along coasts and return to these islands to nest. In doing so, eiders may transport marine nutrients to the terrestrial environments through excretion. These nutrient inputs may have an influence on primary productivity, trophic structure, and overall biodiversity of islands. Using stable isotope techniques, I show that nutrient subsidies from eiders to these colony islands are substantial, and have the potential to have ecosystem-level effects.