Lead Toxicity in Mute Swans

RESULTS
Blood levels
Blood lead levels varied depending on the degree of exposure to
lead, and were significantly lower (P < 0.001) at 'country' sites
(Malahide, Killarney and Shannon), reflecting the expected lower levels
of lead (Table.l). At these sites, only 4.5% of samples showed
elevated lead levels (i.e. > 3.00ugPb/ gHb) with 82% of samples less
than 2.00ugPb/ gHb (Fig.2). A significant increase in blood lead level
was found in birds sampled in urban areas (Galway and Belfast) where
17% of birds had elevated lead. There was a noticeable increase in the
class 2.00 - 3.00ugPb/ gHb from 13.50% at the country sites to 27.50%
at the urban sites (Fig.2).
It is presumed that at least one of these
birds had ingested lead weights since, when it was found dead a few
months later with ingested anglers' weights in it's gizzard, it had a
whole blood lead value of 62.00ugPb/ gHb.
At Cork Lough, values of blood lead differed significantly from
samples from other sites (P < 0.001), the proportion of samples with
high lead levels being much greater (see Fig.2).
Forty two percent of
birds sampled, were suffering from acute lead poisoning (i.e. >3.00ug
Pb/ gHb).
This sample constituted over 90% of the birds at the Cork
Lough. The range of the values was wide (0.46 - 106.30ugPb/ gHb).
Post-mortem results
A total of 101 dead or moribund Mute swans, mostly from Co.Cork and
Lough Neagh, and four Whooper swans from Kilcolman Wildfowl Refuge,
Co.Cork, were examined (Table II). Four categories of birds could be
identified at post-mortem:
- 66 -
i