European raptor populations suppressed by lead poisoning from gun ammunition – new study

Press release from Cambridge University (16th March 2022)

Birds of prey populations across Europe suppressed by lead poisoning from gun ammunition – study

  • Toxic lead ammunition used by hunters has long been shown to kill raptors – or birds of prey – by contaminating their food.
  • New study uses data on lead levels in the livers of thousands of dead raptors to calculate the impact of lead poisoning on their population size.  
  • Europe is missing at least 55,000 adult raptors because of lead poisoning, with populations of White-tailed Eagles 14% lower and Golden Eagles 13% lower than they would otherwise be.

[A white-tailed eagle, one of the species most affected by toxic lead poisoning, feeding on a carcass. Photo by Vasily Fedosenko]

Poisoning caused by preying on or scavenging animals shot by hunters using lead ammunition has left the populations of many raptors – or birds of prey – far smaller than they should be, according to the first study to calculate these impacts across Europe.   

When birds like eagles and Red Kites scavenge carcasses or eat injured animals with fragments of toxic lead from gun ammunition embedded in their bodies they can become poisoned, suffering slow and painful deaths. Smaller doses have been shown to alter behaviour and physiology.

Now, scientists from the University of Cambridge have used data on lead levels in the livers of over 3,000 raptors found dead in more than a dozen countries to calculate the extent to which poisoning by lead ammunition has affected Europe’s raptor populations.

Researchers estimate that, for ten raptor species, poisoning from lead ammunition alone has resulted in an absence of around 55,000 adult birds from European skies.

Worst affected are species like eagles that are naturally long-lived, rear few young per year and breed later in life. However, even populations of species familiar to bird-watchers across countries like the UK, such as the Common Buzzard and Red Kite, would be significantly bigger were it not for lead ammunition.

For example, the study suggests that Europe’s White-tailed Eagle population is 14% smaller than it would have been without more than a century of exposure to lethal levels of lead in some of its food.

This is closely followed by the Golden Eagle and Griffon Vulture with populations 13% and 12% smaller than they would otherwise have been. Northern Goshawk numbers are 6% smaller, and both Red Kite and Western Marsh Harrier populations are 3% smaller.

Common Buzzard populations are 1.5% smaller, but this equates to almost 22,000 fewer adults of this widespread species, say the researchers.  

They estimate that the overall European population of ten raptor species is at least 6% smaller than it should be, solely as a result of poisoning from lead ammunition. The findings are published today in the journal Science of the Total Environment.   

The scientists say that a range of alternatives to lead shotgun cartridges and rifle bullets are widely available to hunters and work well. However, efforts by UK hunters’ organisations to instigate voluntary bans on lead shot in hunting have had almost no effect.

Research by the same Cambridge authors published just last month shows over 99% of pheasants killed in the UK are still shot with lead, despite hunting groups urging members to switch to non-toxic gunshot in 2020, with the aim of phasing out lead use by 2025.

The continued blanket use of lead ammunition means that hunting as a pastime simply cannot be considered sustainable unless things change,” said lead author Prof Rhys Green, a conservation scientist at the University of Cambridge and RSPB.

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

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.”

Currently, only two European nations – Denmark and the Netherlands – have banned lead shot. Denmark plans to follow this up with a ban on 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 oppose this, according to researchers.

Some raptors 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 the opportunity arises, 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 shot in their bodies. Injured ducks or pigeons are less likely to be able to evade predatory birds.

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,” said study co-author Prof Debbie Pain from the University of Cambridge.

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.

For the latest study, researchers used population modelling to calculate how big Europe’s raptor populations would have been were it not for the destructive impact of a single “additional mortality factor”: lead poisoning from ammunition.    

They took data gathered since the 1970s from the livers of thousands of dead raptors in 13 nations and tracked the relationship with “hunter density”: average numbers of hunters per square kilometre in each country, using data from the European Federation for Hunting and Conservation.

Unsurprisingly perhaps, places with a higher density of hunters had more poisoned raptors. Scientists used this relationship to predict rates of poisoning in countries without data from bird livers, but where “hunter density” is known. Their results indicate that a country with no hunters using lead ammunition would have virtually no lead-poisoned raptors.

Scientists say their estimates are conservative, not least as data on poisoned raptors is limited and hugely difficult to gather. For many European raptor species, including some of the rarest ones, there were insufficient data to estimate how great the risk is.

ENDS

The full paper is due to be published online today and when that happens I’ll post a link to it here. [Update: read the paper here]. Meanwhile, here is the paper’s citation and abstract:

5 thoughts on “European raptor populations suppressed by lead poisoning from gun ammunition – new study”

  1. Very interesting. Yet more scientific evidence to indicate that lead ammunition should be banned. I wonder, but can imagine, how the dark side will react to this especially the SGA. No doubt the authors of the paper will come in for some criticism and abuse from those that understand the countryside and who obviously know better!

  2. The damage that continues to be done by a tiny proportion of our population by an almost neanderthal and illogical stubborness in changing lead shot to a less damaging metal is tragic. Tragic not only for our birds of prey but also tragic for the pollution concentrated around Driven Grouse Moor Shooting Butts which has seen an accumulation of lead shot deposited there over centuries… and damaging the very bird they are to shoot as they use the lead as grit to help digest their diet. It’s a malign gift that keeps on giving over generations as it is recyckled thgrough the corposes of these birds who die from it.
    This must lead on to the conclusion that the 13 or so per cent reduction in birds of prey in some way justifies the damage done to their red grouse.
    it’s time they were taken to task on this and lead banned globally in the context of it’s use in hunting .. and beginning in the UK.
    (Posthumous apologies to neanderthals)

  3. No surprise and totally predictable. Will the government now act to ban lead shot? I doubt it – the gun lobby is far too influential. It is of course a disgrace.

  4. It’s been known for some time that lead ammunition in carcases and discarded organs produced by hunting are a major impediment to the expansion of the wild Californian Condor populations re-established after incredibly hard work and expense in both California and Arizona. I seem to recall Trump reversed several statutes banning lead ammunition for hunting when he was in office. That really fits with the ‘man’ doesn’t it? The Wildfowl and Wetland Trust came in for a tremendous amount of flack when they publicised their projections on wildfowl loss due to lead poisoning a few years ago, even though these were based on careful research https://www.wwt.org.uk/our-work/projects/tackling-lead-ammunition-poisoning/ . If ‘recycled’ rapidly by scavenging then that would mean that’s why we don’t see as many dead ducks, geese and swans lying around as we might expect from those high figures. If you wanted to deliberately poison sea eagles there would surely be fewer certain methods of doing so than by having lead shot riddled ducks and geese floating either incapacitated or dead on the water’s surface.

    A wee social note is required here I think. It’s getting on for forty years now since when I was a teenage angler in the early/mid eighties that the use of lead shot to weigh down fishing line was in the very active process of being phased out leading up to a full legal ban being brought in – nearly forty years ago!!! That the vastly greater source of lead entering the environment from shooting has still not stopped speaks volumes. Lead shot was used in what was actually known technically as coarse angling, coarse because it was once pursued almost solely by the lower classes although the official (condescending) reason was that it required less skill than the more upmarket fly/game fishing associated with the Tweed set. If lead shot had been used in their fishing by the latter instead of by miners, factory workers and steel makers going for roach on the local canal then what are the bets it would still be legal as it is ludicrously with shooting partridge, pheasant and of course ‘the grice’.

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