Don't let barn owl become a late, late species

Another Life:On an unspeakable evening in November 2002, a night when the drains of Dublin failed, rush-hour commuters were huddled at dusk on the platforms of Pearse Street station.

Suddenly, and noted only by a few, a barn owl flew in from the deluge, perched on a girder under the roof, and shook itself into composure. If its appearance seemed improbable in 2002, it would be even more so today, as the dockland of old stone warehouses and grain mills is finally morphed into office blocks and penthouses.

In Ireland as a whole, indeed, the barn owl (Tyto alba) is on the way to becoming - literally - a late, late species. After long decline, a survey in the mid-1990s found 130 active nest sites in the Republic. Over the past year, in a conservation project by BirdWatch Ireland, the sites were revisited and only 25 were confirmed as still active. After further survey work and a lot of publicity, the figure has crept up towards 50. In Northern Ireland, too, that is about the total of surviving pairs.

Barn owls have a vast and mostly warm- climate distribution across the world, hunting through tropical coffee plantations, Mediterranean maquis, African savannah, Australian spinifex and Asian palms. They were lured north into Europe by human grain-growing, with its associated rodents and warm roof-spaces. In the era of the horse, spilled grain for rats and mice was everywhere in town and country: owls roosted in the tower of St Patrick's Cathedral and hunted mice and moths in St Stephen's Green.

Their range has since decreased in Europe generally, often drastically and for much the same reasons: intensive farming, loss of foraging habitat, new rodent poisons, loss of hollow trees, changing rural buildings and busy road traffic at night. In Ireland, however, Tyto alba has an extra handicap. While Britain can offer field voles and common shrews as staple diet, these little mammals failed to reach Ireland, and our owls depend mainly on field mice, young rats, and some birds and frogs. If winter floods become the norm of Ireland's climate change, whole communities of field mice and pygmy shrews will be drowned and lost to them.

As rough grassland dwindles and autumn grain stubbles are promptly ploughed again, rodents feed in the last seed-rich margins of roadside verges. Hunting them there, owls are blinded by headlights and struck by lorries. Foraging around farms, they pick up poisons designed for "super-rodents". More and more of the birds are carrying second- generation anticoagulant poisons in their bodies and, as recorded in the Northern Ireland Species Action Plan, "Typically, it takes six to 17 days for a barn owl to die after eating three mice containing Brodifacoum". The Environment and Heritage Service plan urges farmers to go back to Warfarin where rats have not become resistant to it, and the owl is now a priority in the North's agri- environment incentive schemes. British research suggests, for example, that where a breeding pair of barn owls depend on food from rough grassland, they need at least 15km of five-metre-wide field margin along riverbank, woodland edge and field edge within a three-kilometre radius of their nest. But this is based on British owl diets.

In the Republic, most research has focused on owl numbers and diet, rather than on habitat and foraging needs. That's understandable, given that owls are mainly nocturnal and hard to watch, but leave regurgitated pellets around to show what bones, fur and feathers they have swallowed.

Conservation programmes by BirdWatch Ireland and the Irish Raptor Study Group have provided dozens of artificial nest-boxes to make up for those lost from traditional sites. But these need to be placed with a proper understanding of how barn owls use the Irish countryside. When the food supply is good, the birds often lay a second clutch, and this could be a key to the species' recovery here.

Thus, this spring, the male owl in as many breeding pairs as possible will have a leg-ring fitted with a tiny, lightweight radio transmitter, to track its night movements as it hunts food for the chicks. This is the project of John Lusby, already active in the BirdWatch owl programme and now a PhD student with UCC's Dr John O'Halloran.

Based at BirdWatch Ireland's midland office in Crank House, Banagher, Co Offaly, Lusby has spent a year installing 20 barn owl nest-boxes, mainly in Offaly, Galway and north Tipperary. For tracking and allied research, he needs as many opportunities as possible.

Many private individuals have also put up nest-boxes and Lusby would be glad to know of them - or, indeed, any regular barn owl sightings (e-mail: jlusby@birdwatchireland.ie; tel: 05791-51676).