Lead poisoning is still a major cause of death among swans, ducks and other waterfowl despite legislation aimed at restricting the use of toxic lead pellets by shotgun owners, a study has found.
A third of wild waterfowl sampled at four wetland sites in Britain showed signs of lead poisoning which accounted for at least 12 per cent of deaths among waterbirds over the past decade, scientists said.
A single shotgun cartridge contains up to 300 tiny lead pellets most of which fall to the ground after being discharged, where they can be ingested by ducks, geese and swans when feeding.
Lead poisoning in waterfowl affects the nervous system of birds and results in paralysis of stomach muscles leading to starvation and death. The study found that gunshot pellets are the most likely cause of lead poisoning in waterfowl.
Conservationists at the Wildfowl and Wetlands Trust (WWT) in Slimbridge, Gloucestershire said that measures introduced a decade ago to restrict the use of lead pellets near important wetlands and sites of special scientific interest are not working, with many shotgun owners admitting that they flaunt the rules.
“Despite the law, brought in over a decade ago to protect wetland birds, nothing has changed. Clearly an effective solution is long overdue,” said Martin Spray, chief executive of the WWT.
Lead is a highly toxic substance that can affect virtually every part of a bird’s body yet it is still legal to use lead shot in Britain for shooting over farmland and moorland where it accumulates in the environment.
Chris Perrins, a distinguished ornithologist at Oxford University and the Queen’s Warden of the Swans, said that the Royal Commission on Environmental Pollution recommended in 1983 that lead shotgun pellets should be phased out with shooters using “non-toxic” alternatives, such as steel shot.
“Yet here we are nearly 30 years on and we are still using them…We don’t need lead and yet we’re increasingly adding lead to the environment year by year,” Dr Perrins said.
It is estimated that during the early 1990s about 160 tonnes of lead fell to the ground in the UK from spent shotgun pellets, with about 1.6 billion pellets deposited in the wetlands alone. Lead shot can persist for hundreds of years and are readily ingested by waterfowl when the pellets are mistaken for food or grit.
Tests on nearly 300 waterfowl sampled at four sites in Britain during 2010 and 2011 found that 34 per cent of them had elevated levels of lead in their bloodstream, said Debbie Pain, leader of the study published in the European Journal of Wildlife Research.
“Our results indicate that lead poisoning has continued to affect a wide range of British waterbirds long after legal restrictions were introduced,” Dr Pain said.
Fourteen species of ducks, geese and swans were found to have been killed by lead poisoning. Postmortem tests revealed that the gizzard of some birds contained up to 438 pieces of lead shot, the scientists found.
Lead shot was banned for angling from 1988 but only limited restrictions have been placed on shooting, mostly relating to bans over foreshores and certain sites of special scientific interest, and for the shooting of all ducks, geese, coot and moorhen.
However, in 2002 two thirds of ducks being sold by game dealers were found to have been shot with lead, with similar levels revealed in another survey in 2010. “This revealed a disturbing and damaging lack of compliance,” admitted the British Association for Shooting and Conservation, which represents the shooting fraternity.