70
tissue lead levels in wildfowl before and after bans on the use
of lead gunshot for wildfowl hunting (e.g. Samuel and Bowers
2000, Stevenson et al. 2005), or in areas where lead gunshot
may be used vs areas where only non-toxic gunshot may be
used (e.g. Franson et al. 2009). Scheuhammer and Dickson
(1996) investigated the geographical pattern of elevated lead
concentrations in several thousand wing bones from young-
of-the-year ducks collected in Canada to investigate their
relationship with activities known to cause environmental
lead contamination, i.e. waterfowl hunting, non-ferrous metal
mining/smelting, and urban/industrial development. Ingestion
of spent-lead gunshot was the likely primary source of elevated
lead exposure for wild ducks in Canada. In areas of significant
waterfowl hunting, a widespread pattern of elevated bone-lead
was found, rather than fewsmall local sites of high leadexposure.
However, lead contamination of bones of young ducks was
significantly correlated with proximity to metal mining sites; this
accounted for about a quarter of the total area characterised by
a high incidence of elevated lead exposure.
These studies support ammunition-derived lead as the major
source of widespread lead exposure.
INGESTION OF AMMUNITION DERIVED LEAD IN
THE TISSUES OF DEAD OR LIVE GAME SPECIES
(EXPOSURE ROUTE 2)
Many bird species worldwide, including New and Old World
vultures, eagles, kites, buzzards, caracaras, gulls and corvids,
frequently scavenge tissue from carcasses of dead vertebrates
and parts of their bodies discarded by hunters. Predatory birds
that may consume, and perhaps select, wounded animals
carrying ammunition include species from the same taxonomic
groups, but also include owls, falcons and a wider range of
accipitrid raptors. In the UK, red kite Milvus milvus, golden eagle
Aquila chrysaetos, white-tailed eagle Haliaeetus albicilla, buzzard
Buteo buteo, raven Corvus corax, carrion crow C. corone , hooded
crow C. cornix and magpie Pica pica are the bird species most
likely to scavenge from carcasses or discarded viscera of game
animals. All species of raptors and owls could potentially kill and
feed upon a game animal with fragments of lead ammunition
shot into its tissues. Because they frequently prey upon
waterfowl which may be contaminated with embedded lead
gunshot (Table 1), western marsh harriers Circus aeruginosus
and peregrine falcons Falco peregrinus (which prey upon a wide
range of medium sized birds) are the raptor species whichmight
be expected to be most exposed to ammunition-derived lead
via this route.
Ingestion of lead ammunition or ammunition fragments by
predatory and scavenging birds has been reported for decades.
Some of the earliest studies involved the poisoning of bald
eagles Haliaeetus leucocephalus, which frequently feed on
wildfowl in the USA (Kaiser et al. 1979, Feierabend and Myers
1984, Reichel et al. 1984), golden eagles (Craig et al. 1990) and
the California condor Gymnogyps californianus, a Critically
Endangered species whose remaining small population in
the wild was almost driven to extinction by lead poisoning
caused by scavenging upon discarded viscera and carcasses
of unretrieved large game animals such as deer (Rideout et al.
2012). Numerous studies have reported ingested ammunition-
derived lead in white-tailed eagles (e.g.Kenntner et al. 2001 in
Germany and Austria, Helander et al. 2009 in Sweden), and in a
proportion of the carcasses of both this species and of Steller’s
sea eagles Haliaeetus pelagicus and mountain hawk eagles
Spizaetus nipalensis in Hokkaido, Japan (Saito 2009).
Examination of regurgitated birds’ food pellets provides
additional information on the frequency of ingestion of
remnants of lead ammunition. X-radiographs of regurgitated
food pellets from a roost site of red kites in the English Midlands
found that a minimum of 2% contained lead gunshot (Pain et al.
2007). Since the study area included estates on which partridges
and pheasants were shot with lead gunshot, scavenging of
unrecovered shot birds or of wounded birds that died later
could have been a route by which the red kites obtained the
lead gunshot. Other studies have found that the frequency of
occurrence of gunshot in regurgitated pellets is higher during
than outside the hunting season. These include studies of
westernmarsh harriers in France (Pain et al. 1997), easternmarsh
harriers Circus spilonotus in Japan (Hirano et al. 2004) and white-
tailed eagles in Sweden (Helander 1983).
Mateo et al. (2013) reviewed information on lead gunshot
ingestion and lead poisoning in Spain, and reported the
presence of lead gunshot in regurgitated pellets from red
kites (in central Spain and Doñana), Egyptian vultures (in the
Canary Islands), western marsh harriers (from the Ebro delta and
Doñana), Spanish imperial eagles Aquila adalberti (from central
Spain, Castilla-La Mancha and Doñana) and peregrine falcons (in
Doñana). These authors reported that the incidence of ingestion
of lead gunshot by the Spanish imperial eagle in Doñana varied
between years in relation to goose hunting pressure, which in
turn varieswithwater levels in theprotected areas. For additional
information on lead gunshot ingestion and poisoning of raptors
in Spain see Mateo et al. (2007), and also Cerradelo et al. (1992),
Deborah J. Pain, Ruth Cromie & Rhys E. Green