The mute swan is undergoing a remarkable recovery after decades of being poisoned by Britain's anglers, according to a national census of the birds.
The breeding success of the Cygnus olor during the late 1980s has more than replaced the thousands that died from lead poisoning and is causing a comeback at many of their traditional haunts. Before lead fishing weights were banned in 1987, thousands of the swans were thought to be dying each year as a result of swallowing the lead that collected in the mud on the bottoms of rivers and lakes.
The survey of mute swan numbers carried out during the early summer of 1990 shows that the birds are flourishing and population levels are higher than they have been for at least 40 years. On some of England's lowland river systems, most notably the Thames, Trent and Warwickshire Avon, numbers have as much as tripled since 1983, when the last census was taken, according to Simon Delany, special surveys officer for the Wildfowl and Wetlands Trust.
The survey was commissioned by the Nature Conservancy Council and full details of findings will be published early in 1992. "There has been an undoubted increase in numbers throughout the country of between 40 and 50 per centâ•” and we believe that the cause has almost certainly been the ban on lead weights," Mr Delany said.
