72
early part of the non-hunting seasonwill still contain appreciable
amounts of lead acquired during the hunting season.
Widely available reference works summarise observations of
the principal food sources of mammals and it is apparent that
many mammal species worldwide frequently scavenge tissue
from carcasses of dead vertebrates and parts of their bodies
discarded by hunters (e.g. see Legagneux et al. 2014). Badger
Melesmeles, red fox Vulpes vulpesand pinemarten Martesmartes
are the mammal species in the UK most likely to scavenge
from these sources. We are not aware of direct observations of
ingestion of ammunition-derived lead fragments by scavenging
or predatory mammals in the UK. However, it seems probable
from the feeding behaviour of many species, in which large
chunks of meat and some bone fragments are swallowed, that
some ingestion of remnants of ammunition occurs.
INGESTION OF CONTAMINATED SOIL, WATER OR
BIOTA (EXPOSURE ROUTE 3)
Field studies provide evidence that where lead levels of soil, water
and/or biota are elevated as a result of the degradation of lead
from ammunition, there is likely to be uptake of lead by certain
invertebrate and vertebrate animals, with higher tissue lead
concentrations in animals from contaminated than control sites
(Ma 1989, Stansley and Roscoe 1996, Vyas et al. 2000, Hui 2002,
Migliorini et al. 2004, Labare et al. 2004, Heier et al. 2009, Bianchi
et al. 2011). Few studies have been conducted in the UK, but
Sneddon et al. (2009) found that tissues of earthworms (washed
and retained until their bowel was empty before assaying) from
a shooting woodland in Cheshire were significantly higher in lead
(111.79mg/kg) than in those fromthe controlwoodland (5.49mg/
kg). Mixed washed and unwashed small mammal hair showed no
significant variations in lead levels between these sites.
ESTIMATED IMPACTS OF LEAD FROM
AMMUNITION ONWILD BIRDS AND
OTHERWILDLIFE IN THE UK
ESTIMATED ANNUAL MORTALITY IN WILDFOWL AND
TERRESTRIAL GAMEBIRDS IN THE UK FOLLOWING
DIRECT GUNSHOT INGESTION (EXPOSURE ROUTE 1)
The physiological effects of lead in wild birds and pathways by
which ammunition-derived lead reaches them are described
in foregoing sections. Here we estimate, broadly, the numbers
of wildfowl and terrestrial gamebirds in the UK likely to suffer
morbidity and welfare effects and to die from poisoning by
ammunition-derived lead.
WILDFOWL
Data are sufficient to allow us to make rough estimates of
annual mortality in wintering wildfowl in the UK, although with
relatively low precision.
To do this, we used the average proportions of birds with
ingested gunshot provided in Table 3 for the UK, and only
estimated mortality for the species with data presented in this
Table. The incidence of gunshot ingestion in swans cannot be
estimated from hunter-shot birds because they are protected
species, but data do exist for found-dead swans. To estimate
an expected value for hunter-shot swans, we used data for
all of the non-swan species (Table 3), and calculated the
average percentages of hunter-shot and found-dead birds
with ingested gunshot. For hunter shot birds this was 3.2%
(155 of 4,857 birds) and for found-dead birds was 5.2% (59 of
1,129 birds). We then used the ratio of these (3.2/5.2; 0.62) to
estimate what might reasonably be expected as the incidence
of ingested gunshot in swans, had they been ‘hunter-shot’(this
was 3% for mute swan, 8.1% for Bewick’s swan and 14.6% for
whooper swan – Table 3).
British wintering population estimates for the species in Table
3 were taken fromMusgrove et al. (2011), i.e. 2,356,100 birds. By
multiplying the incidence of ingestion by species population
sizes we estimate that 82,313 birds (3.5%) would have ingested
gunshot at any one time, assuming that proportions are
similar to those given for hunter-shot birds in Table 3. We used
the method of Bellrose (1959) to estimate mortality from the
incidence of ingested gunshot. We assumed the proportions
of birds with different numbers of ingested gunshot (i.e., 1, 2,
3 etc.) to be similar to that reported by Mudge (1983) in the
UK. Mudge reported numbers of gunshot ingested by 12
of the 16 species in Table 3, and we have averaged these for
our calculation, i.e. 54% of those birds with ingested gunshot
had just one gunshot, 15% had 2 gunshot and so on (Table
5). We adjusted the proportions of birds with each number of
ingested gunshot using Bellrose’s estimates of hunting bias,
because birds that have ingested lead gunshot are more likely
to be shot by hunters, presumably due to their weakened state.
We used the same hunting bias corrections as Bellrose, based
upon his experimental work on mallard (Table 5). We also used
Bellrose’s method to correct for the effects of turnover. Bellrose
Deborah J. Pain, Ruth Cromie & Rhys E. Green