Why birds of prey are dying from lead poisoning

By Gwyn Wright via SWNS

Birds of prey numbers across Europe are far lower than they should be because of lead poisoning from ammunition, according to a new study.

Scientists from the University of Cambridge, England have found toxic lead from guns left in the animals that birds of prey eat, which ends up killing the birds.

When birds such as eagles and Red Kites, eat fragments of the toxic lead in large doses they become poisoned and suffer slow and painful deaths.

Lower doses of the toxin can change the birds’ behavior and physiology.

The researchers estimate lead poisoning alone has led to an absence of around 55,000 birds from Europe’s skies.

Species such as eagles that have a high life expectancy have few young per year, and breed later in life are particularly badly affected.

However, species loved by bird-watchers across Britain, such as Red Kites and Common Buzzards, would also be more numerous if it were not for lead ammunition poisoning.

It is believed Europe’s white-tailed eagle population is 14 percent smaller than it would have been without more than a century of exposure to lethal levels of lead in some of its food.

Golden Eagles and Griffon Vultures are also fewer in number than they would have otherwise been- with populations being 13 and 12 percent smaller than they would have been.

Northern Goshawk numbers are six percent smaller, and both Red Kite and Western Marsh Harrier populations are three percent smaller than they should be.

While Common Buzzard populations are just one and a half percent smaller, this equates to almost 22,000 fewer adults of this widespread species, the researchers say.

They estimate that the overall European population of ten raptor species is at least six percent smaller than it should be, solely as a result of poisoning from lead ammunition.

For the study, the scientists used data on lead levels in the livers of more than 3,000 birds of prey found dead in more than a dozen countries to work out how much damage the poisoning had caused.

The team, who worked with researchers in Germany, then used population modeling to work out how big Europe’s bird populations would have been without the impact of lead ammunition poisoning.

They took data gathered since the 1970s from the livers of dead birds of prey in 13 countries and tracked the relationship with ‘hunter density,' the average numbers of hunters per square kilometer in each country, using data from the European Federation for Hunting and Conservation.

More poisoned birds of prey were found in places with a higher density of hunters.

The scientists then used this relationship to predict rates of poisoning in countries without data from bird livers, but where “hunter density” is known.

Results indicate a country with no hunters using lead ammunition would have almost no lead-poisoned raptors.

The team says their estimate is likely to be an underestimate given how limited and difficult to gather data on poisoned birds of prey and the fact there was not enough data to work out how great the risk is to many European species.

The researchers say a range of alternatives to lead shotgun cartridges and rifle bullets are widely available to hunters and work well.

However, efforts by British hunters’ organizations to instigate voluntary bans on lead shot in hunting have had almost no effect.

The same team last month found more than 99 percent of pheasants killed in the UK are still shot with lead, despite hunting groups having urged members to switch to non-toxic gunshot with the aim of phasing out lead use by 2025.

Only two European nations, Denmark and the Netherlands, have banned lead shot.

Denmark plans to soon ban lead rifle bullets.

Both the European Union and the UK are considering legal bans on all lead ammunition due to effects on wildlife and the health of human consumers of game meat, but many hunting groups are opposed to it.

Some birds of prey are poisoned when they scavenge from dead animals killed with lead ammunition.

This can be a whole carcass lost or abandoned by hunters, or, for example, the guts of a hunted deer, discarded to reduce carrying weight.

As well as vultures, which rely on scavenging, many other raptors also scavenge when they get the opportunity, including eagles, buzzards and kites.

Many dead pheasants at UK roadsides carry lead shot and fragments in their bodies and are scavenged by buzzards and kites.

Other species, such as falcons and goshawks, are exposed through preying upon live animals with lead embedded in their bodies from being shot and injured but not killed.

X-ray studies of wild ducks in the UK have shown that about a quarter of live birds have lead shot in their bodies.

Injured ducks or pigeons are less likely to be able to evade predatory birds.

Lead study author Professor Rhys Green said: “The continued blanket use of lead ammunition means that hunting as a pastime simply cannot be considered sustainable unless things change.

“Unfortunately, efforts to encourage voluntary shifts away from lead shot have been completely ineffective so far.

“The kinds of reductions in raptor populations suggested by our study would be considered worthy of strong action, including legislation, if caused by habitat destruction or deliberate poisoning.”

Study co-author Professor Debbie Pain said: “It’s taken decades for researchers from across Europe to amass sufficient data to enable us to calculate the impacts of lead poisoning on raptor populations.

“We can now see just how substantial population impacts can be for some of our most charismatic and vulnerable species – species that are protected by EU Regulation and the UK Wildlife & Countryside Act.

“The avoidable suffering and death of numerous individual raptors from lead poisoning should be sufficient to require the use of non-toxic alternatives. These population-level impacts make this both doubly important and urgent.”

The findings were published in the journal Science of The Total Environment.