Lead Toxicity in Mute Swans

I
of the gizzard and oesophagus and distended gallbladder.
In the case
of the Whooper swans, two of the birds showed impaction of food from
the beak to and beyond the gizzard, with a further 130g of grass and
food impacting the duodenum.
A number of moribund birds with symptoms
of lead poisoning were observed prior to death.
Symptoms included
abnormal carriage of neck, lethargy, inability to fly for four to five
weeks prior to death and poorly orientated movements.
There was no significant difference (Mann Whitney U) between the
weights of lead poisoned and other dead swans.
The observed ratio of
sexes in lead poisoned swans did not differ (X 2 , P > 0.05) from the
normal population ratio of 54% males:46% females.
More adults than
2
juveniles died from lead poisoning than expected (X, P< 0.001).
Most lead poisoned swans died in winter.
In the Cork Lough
catchment, 14 birds died from lead poisoning between November and
March, but only six birds died of lead during the other months, though
the large sample from Lough Neagh (n=49) greatly influences the overall
data (Table III).
Of birds X-rayed, 27% (of 41) had lead in their bodies (Table IV).
Three had been sprayed with shotgun pellets but this shot-in lead did
not cause any elevation in blood lead level (Table IV).
Ingested
pellets in contrast, caused an increase in 'whole blood lead.
Nevertheless two birds, (Table IV) though positive for lead, showed no
increase in blood lead.
Eight birds, which had no pellets in their
gizzards, had elevated blood lead values ranging from 3.10 ugPb/ gHb to
5.20 ugPb/ gHb. Five of these birds had histories of elevated lead (as
recorded from a number of previous blood samples).
One bird when
X-rayed was shown to have seven pellets in it's gizzard, but after
death a week later, post-mortem revealed 11 pellets. X-ray of gizzard
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