The immediate effects of marine oil spills on seabirds in the vicinity of the spill are well known, and large-scale mortality resulting from fouling of plumage and ingestion of oil have been well documented. However in addition to acute lethal effects, populations may experience longer-term sublethal effects of ingested hydrocarbons. These have potentially profound consequences for productivity and population dynamics, but there are very few data to allow a proper assessment of the likely impacts of these factors on different species.