(as they have larger body size), although they can ingest very

large numbers of gunshot (Newth

et al.

2012). As lead poisoning

was the diagnosed cause of death in a quarter of migratory

swans found dead (Newth

et al.

2012), overestimation in these

species seems unlikely. Had there been widespread compliance

with regulations banning the use of lead gunshot for shooting

wildfowl (and over certain wetlands) in England, this estimate,

based upon data from before the ban, might overestimate

the numbers affected currently. However, compliance with

English regulations banning the use of lead gunshot for

shooting wildfowl has been shown to be low (Cromie

et al.

2010, 2015) with some 70% or more of ducks shot in England

and purchased through game outlets being illegally shot with

lead ammunition. Hence, legal and illegal deposition of lead

gunshot in wetland and terrestrial wildfowl feeding habitats is

likely to have continued at broadly similar levels to the period

before the ban. Similarly, Newth

et al.

(2012) found that the

proportion of birds dying from lead poisoning in England did

not change significantly after the introduction of legislation.

For this reason the estimate of number affected is likely to be

approximately correct.

While there are various assumptions and uncertainties in this

calculation for wildfowl, we suggest that the true value is likely

to be in the high tens of thousands and probably lie within

the range 50,000-100,000 individuals. More precise estimates

cannot readily be made at this time.

Many more birds are likely to suffer welfare effects from lead

ingestion than die. If all wildfowl predicted to ingest gunshot

suffer welfare effects, this would result in about 15% (Table 5)

of birds,

i.e.

c. 353,000 suffering welfare effects every winter (and

more throughout the year). We therefore estimate that 74,000 –

353,000 individual wildfowl suffer welfare effects every winter.

While it is possible to broadly estimate mortality from lead

poisoning, determining impacts at a population level is

not straightforward. This is especially the case for wildfowl

in the UK, as the majority are migratory and thus subject to

pressures across their ranges. The only reasonably robust way

of doing this is to model and compare alternative population

trajectories for a species based upon demographic rates

estimated when effects of ammunition-derived lead are

present and absent. The long-term and complicated nature of

collecting such information means that for most species, an

accurate assessment of the extent of mortality, and possible

population level effects from lead ingestion, whatever the

source, is currently not possible for most species.

Whendetailedinformationondemographicratesisnotavailable,

it is legitimate to adopt a comparative approach to the detection

of effects of external drivers on population trends (Green 1995).

This involves comparing population trends across species or

populations with differing levels of exposure to ammunition-

derived lead. A negative correlation between population trend

and exposure may be suggestive of population-level effects. At

a European level, Mateo (2009) correlated population trends in

a set of 15 taxonomically similar European wildfowl species with

broadly comparable life-history characteristics with reported

prevalence levels of shot ingestion. There was a statistically

significant tendency for specieswithhigh levels of shot ingestion

to have more negative population trends than species with low

shot ingestion levels. As was pointed out by Mateo, correlation

is not causation and effects of some unidentified factor might

have led to a spurious correlation. Nonetheless, this analysis is

suggestive of an effect of lead contamination on population

trend and indicates that it is worth looking further at the effects

of lead, especially for species with high shot ingestion levels.

TERRESTRIAL GAMEBIRDS

Less information is available for the UK on levels of gunshot

ingestion by terrestrial birds than by wildfowl and it would not

be appropriate to extrapolate levels of mortality in terrestrial

gamebirds from the studies on wildfowl.

However, data on the proportion of terrestrial birds with

ingested gunshot are available for several species in the UK,

i.e.

hunter-shot red-legged partridge (1.4%, Butler 2005

), hunter-

shot pheasant (3%, Butler

et al.

2005) and grey partridge found

dead (4.5%average for adults and juveniles, Potts 2005), so order

of magnitude estimates of mortality can be made. To do this we

took breeding population estimates (fromMusgrove

et al.

2013)

of these species and the other most numerous gamebirds (red

grouse) potentially susceptible to gunshot ingestion and added

the numbers of pheasant and partridge raised in captivity

which are subsequently released for shooting each year (

i.e.

million pheasants and 6.5 million partridges – released in 2004

(PACEC 2006)). To obtain numbers of individuals fromMusgrove

et al.

’s (2013) estimates, we doubled the numbers of territories of

red-legged and grey partridges. For pheasant, we assumed that

the ratio of males to females was 1:4.6 (after the shooting season

(Cramp and Simmons 1980)). We ignored the many young wild-

bred birds hatched in the previous breeding season that are

Deborah J. Pain, Ruth Cromie & Rhys E. Green