Lead Toxicity in Mute Swans

median value of lead in April is similiar to that found by Birkhead
(1983) on the River Thames. It is suggested that increased movement of
birds, particularly adults in search of breeding sites, is responsible
for the lower median value at this time.
The level of lead in moulting birds was particularly low.
At The
Gearagh, the median lead level was 0.84 ugPb/ gHb and no birds were
suffering from lead poisoning.
The Gearagh (Fig. 1) is a country site
with low organo-lead input and although wildfowling is carried out
during the winter, the swans do not seem to ingest lead pellets during
the moult. · The lowest median levels at Cork Lough were al90 during the
moulting period.
It is not known whether lead is mobilised from body
tissues into the plumage of the Mute swan as are other metals in some
birds (see Furness et al., 1986).
Protoporphyrin as a measure of lead exposure
Protoporphyrin IX (FRBCP) has been used for decades as a measure of
lead exposure in humans (Chisolm and Brown, 1975).
Barrett and Karstad
(1971) were the first to adopt this method qualitatively for
waterfowl.
Roscoe (1979) pioneered the use of the direct method of
FRBCP in waterfowl using a haematofluoremeter.
Birkhead (1983) also
employed a haematofluoremeter to detect increased blood lead exposure
in Mute swans on the River Thames.
The 'normal' values of FRBCP in
Mute swans vary greatly and may depend on physiological state
(O'Halloran et al., (B) in press).
The reference distribution varies
from 0.40 - 3.90 ug PPIX/ gHb (0.16 - 1.20 umoles) and values of up to
13.40 ug/ gHb may be recorded in healthy cygnets. Because of the
variation in FRBCP and because the direct method of estimating FRBCP
may detect other disorders in protoporphyrin, this study employed the
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