Lead poisoning from spent gun ammunition is a major cause of death among UK waterbirds, scientists say.
Scientists found 10% of dead waterbirds collected from 1971 to 2010 died from lead poisoning and a third of a sample of living birds were also affected.
They said it showed laws restricting use of lead gunshot were not working.
Shooting groups rejected this saying that few people now used lead gunshot but there was a "historical legacy" of lead shot in the environment.
The study was conducted by the Wildfowl and Wetlands Trust (WWT) and is published in the European Journal of Wildlife Research.