Saturday, 4 February 2012

Roads take toll on Barn Owls

The surprisingly mild conditions that we have seen this winter are likely to have been beneficial for the county’s Barn Owls. Cold weather, in particular periods with snow cover, high winds and prolonged rain, can all cause major difficulties for Barn Owls which, unable to find favoured small mammal prey, soon succumb to starvation. One of the reasons for this is that Barn Owls carry little in the way of fat reserves, something that limits their global breeding distribution to those parts of the World where the winters are less hostile. The northern limit of the Barn Owl breeding distribution falls, for this reason, in northern Scotland. Even here, the species only just hangs on, restricted to lower altitude sites and the population quickly knocked back by a particularly poor winter.

Another major cause of Barn Owl mortality is collision with traffic on our increasingly busy roads. Roads fragment Barn Owl hunting ranges, leaving the birds no choice but to cross them; flying characteristically low they are often hit by a passing car or lorry. One estimate suggests that as many as one in three of the Barn Owls born each year will end up dead on a road. This statistic was brought home to me the other morning when, driving south into Suffolk I came across the corpse of a freshly dead male Barn Owl. This proved to be a young bird, the talon comb on its foot scarcely developed. It is thought that this comb is used in older birds to maintain the plumage, particularly that on and around the all-important facial disk.

It appears that some young Barn Owls may actually be drawn to roads by the small mammal populations supported within the roadside verges. On quiet country roads, these verges can provide important hunting opportunities, particularly where the wider landscape is dominated by more intensive arable. I have seen birds working these verges at various sites across the north of the county, often with great success, judging by the numbers of Field Voles and Wood Mice taken. However, where these verges sit alongside busier stretches of road, then it is often only a question of time before a bird is killed.

With so much bird-ringing activity directed to increasing our understanding of Norfolk’s Barn Owls it is likely that many of the Barn owls found dead on our roads will be carrying a numbered ring. If you come across a dead Barn Owl, please do stop (if you can do so safely) and check. The number of the ring will almost certainly link the bird to a local breeding site and help researchers to build up a picture of where these birds face the greatest risks from our road network.

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