Lead Toxicity in Mute Swans

I
the pellets as they moved in shore to feed on macrophytes.
Clay-pigeon
shooting has ceased since the deaths of 25 swans in 1985 (Table II).
However, metallic lead persists in the environment, as illustrated by
the fact that four more Mute swans died at the same location in 1987,
two years after the last clay-pigeon shoot.
At Kilcolman wildfowl
refuge Co.Cork, the first known case of fatal plumbism in Whooper swans
in Ireland occured following the ingestion of gun-shot pellets
scattered there at least 18 years previously. Beer and Stanley (1965)
reported a similiar situation in a study uf lead poisoning at
Slimbridge where there had been no shooti:1g for almost two decades.
Only two detectable differences were notiLed at Kilcolman in the winter
of 1986/87 from those of previous years.
Firstly, there were more
Whooper swans than previous years, 90 com~ared with 50 in 1981
(O'Halloran, 1981) and secondly, the bird~
spent more time feeding on
potatoes. Whether it was a change in bir~ density and/or a change of
feeding behaviour and hence the need for ::iore grit which caused this
incident to occur is unknown.
In Ireland, there are two main sources of acute lead poisoning in
swans: a) shooting pellets (past and pres~nt) and b) discarded anglers 1
weights.
While urban lead contributes to blood lead in urban birds it
does not cause acute lead poisoning.
Any policy to reduce lead
poisoning in birds in Ireland should cons~der
both past and present
inputs of lead into the environment before any decision is made on the
sighting of shooting sites or the holding of large scale angling
competitions.
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