Posts Tagged ‘Barn Owls 2010’

A most unusual year for Barn Owls

11 September, 2010

These chicks are living proof of how Barn Owls can bounce back after hard times if prey is abundant.
Report by Colin Shawyer, Project Director of the Barn Owl Conservation Network.

Normally the Barn Owl breeding season would be over by now, albeit, perhaps for a few sites which still contained young, a consequence of pairs which had failed earlier and chose to lay a repeat clutch in June or those which were double brooded, having laid again in July.

By August, therefore, most of us will have thought our monitoring rounds were complete. Provisional results at this time indicated fairly high occupancy rates at nest sites situated below 100 m asl although at higher altitudes many sites fell vacant due to the high mortality which had been experienced by Barn Owls from prolonged snow cover during the 2009/2010 winter.

However not unlike 2009, fledging success was once again poor. It barely exceeded an average of two fledged young per successful nest in most regions of England and Wales and was not helped by the gale force winds which ravaged the eastern half of England between 14th and 16th July.

Bad weather for Barn Owls

The winds which lasted three days and nights and which prevented the adults from hunting, caused the death of entire broods many of which were only two weeks from fledging. For example, on 16th July although it was almost impossible to erect the ladder to the outdoor nestboxes I was monitoring in Yorkshire, chicks at many sites were close to starvation weight and I suspect that most were likely to have died by the following day.

In Lincolnshire alone it is believed that this climatic event, almost unheard of at this time of year, caused the loss of between a quarter and one third of owlets, many of which had already been ringed as healthy birds only a week or so earlier.

A Poor Summer

After monitoring hundreds of nestboxes during May and early June, it was clear that although a good proportion of nest sites were occupied by pairs of owls almost a third had not attempted to lay and judging by the relatively low body weights in females at these sites, that they were unlikely to do so later in the year.

At some of these sites the adult females and even some adult males had begun their wing moult. This is a good indicator that they are unlikely to breed and that there would be little value in visiting these particular sites again in 2010.

Good Signs

At a greater proportion of nest sites where pairs were present, however, moulted wing feathers were unusually absent suggesting that the owls may still be preparing to breed.

How important these observations were. Together with my colleagues we began re-visiting these sites in late August and early September, to find healthy well-fed broods of fours, fives and sixes.

The ages of many of these chicks are currently between 4 and 7 weeks of age indicating that eggs had been laid in late June and that the owls must have achieved breeding condition soon after our earlier visits during that month when we had all but given up hope of them breeding. Even at some traditionally-used nest sites where there was no evidence of Barn Owls in early June, large and healthy broods are now present.

At a few sites, Barn Owls are still incubating eggs or brooding small young, most are probably repeat clutches but a few are genuine second attempts, the young of which will not fledge until November.

There is every indication that these late broods will successfully fledge and that when these figures are taken into account, overall breeding success in 2010, will not be as quite as bad as we had originally feared.

Colin Shawyer
BTO – BOMP Project Development and Monitoring
BOCN – Project Director, UK and Ireland

The Barn Owl is specially protected under Schedule 1 of the Wildlife and Countryside Act, making it unlawful to intentionally or recklessly disturb it whilst it is preparing to nest or is at the nest with eggs or young, or to disturb its dependent young.

Inspection of nest sites can only be undertaken by experienced fieldworkers holding a licence issued by the appropriate countryside agency: Countryside Council for Wales, Natural England, Northern Ireland Environment Agency, Scottish Natural Heritage