Lead Toxicity in Mute Swans

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ABSTRACT
A study of blood lead levels in Mute swans Cygnus olor in Ireland
has revealed that ingested lead pellets are responsible for acute lead
poisoning.
Forty two percent of blood samples from 870 live birds at
one site showed elevated lead levels. X-ray examination of live birds
revealed the source of contamination to be ingested lead pellets.
Urban birds were shown to have higher (P < 0.001) lead levels than
rural birds, the blood lead levels of which were presumed to reflect
natural background levels. Urban grass was shown to have elevated lead
but this did not cause lead poisoning in Canada geese Branta
canadensis.
Post-mortem examination has shown that 68% (n=lOl) of all
Mute swans examined from a number of sites died from lead poisoning.
Two sauces of poisoning were identified; spent gunshot from a
claypigeon shooting site at Lough Neagh Northern Ireland and lost or
discarded anglers' weights at Cork Lough and at a fishing pond in
Belfast, N.I. The first known case of lead poisoning in Whooper swans
Cygnus cygnus in Ireland is recorded which resulted from the ingestion
of gunshot used almost two decades earlier. Aspects of the pathology
of lead poisoned swans is discussed.
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