Influence of wintering area on persistent organic pollutants in a breeding migratory seabird

As apex marine predators, seabirds are often sampled to monitor bioaccumulative persistent organic pollutants (POPs) in the marine environment. Despite the restrictions on use and production of many POPs, concern remains about levels of these chemicals present in marine biota due to their potential toxicity. Many seabird species are migratory, and although overwinter- ing area has been hypothesized to affect the accumulation of POPs, few have studied the contri- bution of exposure in the wintering area on the POP burdens of seabirds. This study investigated the impact of wintering area on concentrations and patterns of organochlorines (OCs) and poly- brominated diphenyl ethers (PBDEs) in plasma of breeding great skuas Stercorarius skua from 3 colonies; Bjornoya (Svalbard), southeast Iceland and Shetland (Scotland). To do so, stable iso- tope values of primary feathers grown during the winter were used in conjunction with geolocator data (n = 16) to assign untracked individuals (n = 122), to 3 wintering areas (America, Europe and Africa). Birds wintering in Africa had lower plasma concentrations of many OCs and PBDE 47 compared to the other areas. Nevertheless, the influence of wintering area differed between con- taminants and between breeding colonies. We conclude that although wintering area had a significant effect on both concentrations and patterns of POPs, its influence was small in compar- ison to differences in exposure to these pollutants at breeding colonies, but that accumulation of POPs during the winter may be important for specific populations of seabirds.