There is no effective control over the use of these highly toxic poisons which are widely sold to the general public.
The serious decline in the UK's Barn owl population - to about 30% of levels of barely a generation ago - is deeply alarming to all who love our countryside and its wild birds.
But it's not a case to wring our hands and regret the likely passing of yet another of our iconic wildlife species.
On the contrary - there are compelling reasons to believe that Barn owls are dying for a very specific reason - and it's one that we can reverse.
The villain - new rodenticides
Research carried out on Barn owls across the UK shows that most of the birds contain in their blood and tissues a highly toxic kind of rat poison -Second Generation Anticoagulant Rodenticides (SGARs).
Some birds also die as a direct result of poisoning - typically bleeding to death from internal haemorrhage.
There is little doubt that sub-lethal doses have contributed to the catastrophic decline in Barn owl numbers. The precise effects of sub-lethal doses are unknown although they are highly likely to affect survival and breeding success.
Yet these rodenticides can be bought and used without any training - and product labelling is inadequate and misleading.
SGARs were first introduced in the 1970's when some rodent populations were found to be unaffected by (resistant to) Warfarin-based products.
Since then the proportion of Barn Owls found to contain SGARs has increased from 5% in 1984 to 84% in 2011, and in the last batch of Kestrels examined, all of them were contaminated.
The anticoagulant Warfarin in humans can cause nausea, vomiting, diarrhoea and fever - and SGARs are 100 to 1,000 times more acutely toxic than Warfarin.
Out of control
There is no effective control over the use of these highly toxic poisons which are widely sold to the general public in garden centres and hardware stores, used on 76% of farms and by 75% of gamekeepers.
Although 40% of all SGAR are used by professionals, anyone can set themselves up as a Pest Controller - no licence or qualifications are required.
This was amply demonstrated when BBC Panorama reporter, Simon Boazman posed as a pest controller and bought extremely toxic 'professional use' products without any questions being asked.
How it happens
Many people who use rat poison have no idea about the risk to wildlife and pets and assume that following the 'directions' prevents other species being affected.
In reality, no amount of bait covering makes the slightest difference because poisoned rats and mice take 3-14 days to die. And during this time they carry the poison into the open within their bodies.
When they are eaten by owls and other predators such as foxes and cats, this is termed secondary poisoning.
Baits are often laid even when there is no significant rat problem. This increases the risk of harmless mice and voles ingesting it and passing it on.
Permanent baiting also contributes to rats building up a resistance thus increasing the use of even stronger poisons.
Inadequate and misleading
And the labels on these highly toxic products do nothing to help. Indeed they are downright inadequate and misleading!
Current Directions for Use imply that bait covering, carcass removal, and removal of uneaten bait will adequately protect non-target species but this is simply not true. There is no mention of:
- Secondary poisoning
- The extent of predator contamination ... and the fact that bait-covering cannot prevent it
- That permanent / preventative use encourages consumption by non-target small mammals - which are then eaten by owls, Kestrels and other predators
- That frequent use leads to a build-up of resistance to SGARs in rats
- That poison should only be used as a last resort.
Finally, controls are under review
Controls on the use of SGARs are currently under review by theChemicals Regulation Directorate of the Health and Safety Executive.
This has prompted the Barn Owl Trust to launch an e-petition calling for better labelling and the regulation of the use of these poisons to protect wildlife. The Trust's Campaign Page provides more information on the Petition.
Specifically, the petition asks Government Minister Mike Penning, and the Health and Safety Executive to:
- Regulate SGARs for Last Resort use only - second generation rodenticides (SGARs) must only be used after non-toxic and less toxic control methods have been fully deployed and if a persistent rodent problem is still a significant threat to public health.
- Ban preventative and permanent baiting - the use of rodenticides at times or places where there is no significant rodent problem must be made a breach of statutory conditions of use.
- Include accurate information on all SGAR products - Clearly state the extent of contamination of Barn Owls and Kestrels (84-100%) and the fact that keeping bait covered (although important) cannot possibly prevent secondary poisoning.
The Barn Owl Trust's recommendations are based on scientific research and 25 years of experience in the field, advising farmers, landowners and gamekeepers on more environmentally friendly methods of rodent control (as summarised in the Barn Owl Conservation Handbook).
Barn owls in trouble
Around the turn of the millennium there were approximately 4,000 pairs of Barn Owls in Britain with only one in 75 farms having a Barn Owl nest. This represents a decline of at least 70% on historical levels.
Since 2009 frequent extreme weather events caused a massive drop in numbers and in 2013 the number of nests dropped by 95% in some areas. Even less-affected areas witnessed a 45% drop.
The Barn Owl Trust strongly suspects that rodenticide contamination has been decisive in reducing the species' ability to cope during hard times. Please join our campaign to save Britain's Barn owls.
David J Ramsden MBE is Senior Conservation Officer with the Barn Owl Trust.
Avaaz petition: Save Britain's Barn Owls
Rats can prove a risk to public health and in some areas do need to be controlled. See the Barn Owl Trust's web page - How to control rats as safely as possible - for a guide to minimising the risk to wildlife and pets.