THE INDISCRIMINATE use of poisons to kill rats or mice has been linked to an alarming decline in some of Ireland’s most iconic birds of prey, such as barn owls and kestrels.
According to one of the country’s leading experts, several native species of raptor – the ornithological term for birds of prey – are feeding on contaminated rodents and inadvertently ingesting poisons.
Raptor conservation officer with BirdWatch Ireland John Lusby said substances used in certain rodenticides were extremely toxic and can accumulate within birds.
This type of “secondary poisoning” is thought to be behind a sharp fall-off in the number of barn owls.
Known by their distinctive white plumage and eerie silent flight, the owls have seen their breeding population here plummet by more than 70 per cent in the past 20 years alone.
Recent estimates suggest there are now only between 400 and 500 pairs left in the country.
“In Ireland, we have fewer small mammal species compared to other countries like Britain, so barn owls here depend on rats and mice as prey to a greater extent,” Mr Lusby said.
Ornithologists fear kestrels, still the most commonly sighted bird of prey here, may be on a similar trajectory. The birds, most often spotted in their familiar hovering pose near roadside ditches and fields, share a similar ecology to the barn owl in terms of diet and habitat, and have declined by 7 per cent to 10 per cent since the 1990s.
There are also concerns surrounding the notoriously reclusive long-eared owl, whose cryptic nature makes the species difficult to survey, but whose numbers are also thought to be in decline.
Since 2010, the practice of using poisoned meat baits to control farmland pests such as foxes and crows has been outlawed because of the knock-on effects on other species.
However, there are currently no regulations concerning the use of poisons to kill rats or mice. In Britain, there are restrictions against the use of certain rodenticides in outside areas in order to protect other species, and ornithologists want similar regulations adopted here.
Raptor populations provide a “window to the health of the environment”, Mr Lusby said.
It was the rapid fall-off in peregrine falcon numbers in the middle of the last century which first alerted the authorities to the harmful effects of certain pesticides such as dichlorodiphenyltrichloroethane (DDT).
The build-up of traces of the pesticide in the bird fat tissues as a result of its feeding on smaller insect-eating birds was found to be reducing the amount of calcium in bird’s eggshells, causing the eggs to be crushed by the weight of adults seeking to incubate them.
Since a ban on DDT was implemented, the peregrine population in Ireland, which had dwindled to little more than 60 pairs in the 1970s, has rebounded significantly, and the birds are now no longer a conservation concern.
Because peregrines and sparrowhawks, Ireland’s most common bird of prey, feed primarily on other bird species, they appear to have avoided the risks posed by rodenticides, in contrast with owls and kestrels.
Ireland unfortunately has had a poor record in protecting its native raptor species, arguably the worst in Europe.
There are currently 11 breeding raptor species in Ireland: the sparrowhawk, kestrel, peregrine falcon, merlin, hen harrier, barn owl, long-eared owl, buzzard, red kite, golden eagle, and the white-tailed or sea eagle.
Before the widespread woodland clearances of the 17th and 18th centuries, Irish skies teemed with big raptor species such as eagles, buzzards and goshawks, and perhaps even honey buzzards and eagle owls.
Unfortunately, the fate and ultimate extinction of these birds followed an all too familiar narrative of persecution and habitat destruction.
At one point in the last century, Ireland held the dubious distinction of being the only country in Europe which had more extinct birds of prey than existing species.
Because of our island status, lost species are also less likely to recolonise than in other regions which lie adjacent to healthy population groups.
While the recent high-profile eagle and red kite reintroduction programmes represent a step in the right direction, the breeding populations of these birds here are a long way from being classified as viable.
Perhaps the most positive recent news in raptor circles has been the remarkable comeback of the buzzard. Hunted to the brink of extinction in previous centuries, the broad-winged bird is now found throughout the country.
BirdWatch Ireland has launched a nationwide raptor appeal as part of its long-standing raptor conservation project to halt the loss of iconic birds such as the barn owl.
It is also set to beef up its own monitoring and research programmes on raptors. For more details log on to www.birdwatchireland.ie
RAPTORS AT RISK ICONIC BIRDS FACE A HIDDEN ENEMY:
Merlin– The smallest of all our birds of prey, also known as the pigeon hawk, is reclusive and hard to spot. It is unclear how Ireland's population is faring.
Peregrine falcon– Swiftest bird in the skies. It suffered a catastrophic decline in the middle of the last century, linked to use of pesticides such as DDT. It has since rebounded significantly and is no longer a conservation concern.
Long-eared owl– Now thought to be more common than its barn owl cousin, but nonetheless on the wane because of use of poisons and loss of habitat.
Red kite– Tree-nesting raptor, reintroduced back into Ireland in 2007 after 200 years of absence. There were 14 breeding pairs of red kites in Wicklow as of last year.
Common buzzard– Hunted to the brink of extinction in previous centuries, this broad-winged raptor is now thriving again. Feeds on small mammals and carrion.
Barn owl- Known by its distinctive white plumage and eerie silent flight. Population has been in sharp decline, which experts link to the unrestricted use of rodenticides.
Kestrel– Easily the most commonly spotted raptor, typically seen hovering near roadside ditches and fields. Population is undergoing moderate but continual decline.
White-tailed eagle– Extremely large coastal bird which preys on fish, smaller mammals and carrion. Once widespread in Ireland, but like the golden eagle became extinct in the early part of the 20th century. Reintroduced back into Co Kerry in 2007.
Hen harrier– Scarce summer visitor to upland areas and bogs mainly in western Ireland. The species is steadily declining, probably due to the loss of quality moorland habitat.
Golden eagle– Often confused with buzzards, but much larger, with a wing span up to 6ft. Became extinct in Ireland in 20th century but was recently reintroduced back into Donegal.
Sparrowhawk– Ireland's most common bird of prey, distinguished by its bluish-grey overcoat, often hunts garden birds in towns and cities.
