Has the dwindling barn owl had a shrew too many?

This has become of urgent concern to BirdWatch Ireland’s raptor conservation project, in which Tosh works with John Lusby, a postgraduate researcher at NUI Cork and now the organisation’s raptor-conservation officer.

The barn owl has suffered steady decline in Ireland, its numbers falling by more than half since the 1970s. The conservation team confirmed 133 nest sites last spring, but the national population is now put at 450 to 500 pairs, most of them in the warmer southern counties and a quarter of them in Cork.

Originally it was thought that lack of nest sites was limiting the population, and 250 nest boxes have been installed in recent years in empty barns, castle ruins and other classic locations. However, surveys have found plenty of potential nest and roosting places in many parts of Ireland. And while the known nest sites are the most the research team have located during the project, this year’s rain-soaked breeding season was a bad one for the owls.

Of 80 nests the project monitored, a quarter failed to fledge any young. While a lot of heavy rain can keep the owls from flying, a high rate of mortality and emaciated chicks have marked the productivity of the past three years, especially at nests in south Tipperary. Here the owls have been feeding almost exclusively on greater white-toothed shrews. Is it the lack of pygmy shrews, a food to which the Irish owls are long adapted, that is lowering their breeding success? Research will continue with this in mind.

Montgomery has warned that the changes among small mammals, as the invaders spread, “are likely to reverberate throughout the ecosystem”, changing vegetation, insect communities and the productivity of bird and carnivore predators. The impact on the barn owl could prove the first bitter surprise. Far from improving the barn owl’s diet, the greater white-toothed shrew may have wrecked it.

Eye on Nature Your observations and questions

I have seen a briar growing from the fork in an ash tree, about 15ft up. It is growing downwards, and the tip is now a few feet from the ground. Was it grown from a blackberry dropped by a bird?

C Guckian Dromahair, Co Leitrim

More likely from a seed passed by a bird, which took root in detritus in the fork of the tree.

I saw a blue tit take whole nuts from my feeding baskets and hide them in my hanging baskets under leaves.

Siobhán Hearne Waterford

Some blue tits hoard food, as do some other members of the tit family.

I attach photos of two holes that have appeared, one under the path beside the dog kennel. The other is 13cm in diameter. Both go down about 30cm.

Paul Kerr Barna, Co Galway

They are possibly exploratory rabbit holes.

We seem to have a fox with a fancy for corn on the cob, judging by fox scats with almost entirely undigested corn. The nearest maize field is almost a kilometre away. The fox comes every year for pear windfalls.

Michael McCarthy Bagnelstown, Co Carlow