Lead Toxicity in Mute Swans

Swans
LEAD POISONING IN MUTE S\VANS AND FISHING
PRACTICE IN IRELAND
ABSTRACT
Lead poisoning in waterfowl resulting from the ingestion of spent
gunshot pellets was first recognised in the USA in 1874. Since then,
research in fourteen European countries has shown spent gunshot to be
the cause of considerable bird mortality. In Britain in particular, 'angling
litter' has caused the deaths of thousands of mute swans, Cygnus olor
( Gmelin). The incidence of lead poisoning in Irish mute swans has been
investigated. and blood samples and post-mortem examination have
revealed local elevated lead levels. Blood samples from swans at Cork
City Lough have revealed that 50% of live birds have elevated lead
levels. Although legislation banning the use of lead weights has been
drafted in Britain, no such statute has been considered in the Republic of
Ireland. Six alternatives to lead shot are now commercially availc.ble. Few
scientific data are available on accumulation of 'angling litter' in Ireland;
howL-;-'er, if angling practices resemble those in Britain, it is essential that
available information be collated.
INTRODUCTION
The importance of lead shot from hunters' cartridges as a source of
environmental contamination has been widely discussed, especially in N.
America (Philips and Lincoln 1930), since first discovered in 1874.
Ingested lead shot affects waterfowl in particular, though other species
are not exempt. In the western United States, the Californian condor,
Gymnogyps californicus (Shaw), for example, is becoming extinct with
only six condors remaining in the world (Wilcove and May 1986). 'Lead
has been implicated in this decline, with at least two birds having died in
the last three years from dining on animals that have been shot by
hunters.' The lead levels in the remaining wild condors are alarmingly
high (Wilcove and May 1986). 'Waterfowl appear to be at least twice as
sensitive to the bio-chemical effects of lead ·as are man and other
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