Born in a Barn

One of the farmers participating in The Carrs Wetland HLS schemes was chatting to me on the ‘phone about Barn Owls this week. A pair using a nesting box in his cattle shed on Ings Lane, Staxton have successfully raised 3 chicks to fledging this summer. This encouraging news has inspired me to write this blog post (for which title I apologise, but it was hard to resist.) The young owls apparently have left the nest and have been seen flying about but are currently still spending time near to the nest. The aforementioned farmer tells me that on another farm in the Vale a pair had a brood of seven chicks (though not all may survive) while on another farm he’d heard of a nest fledging five young. Happy news indeed.

Jul11 Flixton brow quarry 002

Arable and pastoral patchwork on The Carrs, seen from Flixton Brow.

Barn Owls seem to do rather well in The Carrs as the mix of arable and pastoral farming, rough grassland along ditches and beside quiet lanes and hedgerows provide good hunting for small mammals. Rough tussocky grassland is the ideal habitat for their prey, with sufficient dead grass or ‘litter’ layer for voles to create hidden runways through it.

Small mammal populations are famously fickle, undergoing cycles of boom and bust which have a powerful influence of the fortunes of birds of prey which rely heavily upon them for food. Barn Owls have a clever strategy to hedge their bets against the vagaries of the weather and food supply. The eggs are laid at 2-3 day intervals but incubated right away and hence hatch on different dates, resulting in a brood of chicks of descending size. In this way a good year for small mammal prey will enable them to raise more of the chicks to maturity but if food is in short supply then the first -hatched chicks will prevail while the smaller, weaker young will perish, thus the size of the brood will naturally adjust according to conditions. It may seem cruel to let fate intervene, but if they always laid a smaller clutch then the birds could not capitalise on a bonanza of Bank Voles or whatever prey items happen to be in abundance.

The wetland project occasionally receives requests to help source owl pellets for school groups to analyse – by dissecting their contents one can identify the types of prey from the tiny jaw and skull bones in the pellets. With a suitable sample size one can derive some interesting statistics about an owl’s diet and by inference about the populations of different prey species. Analysis of a batch of pellets from the Potter Brompton area a couple of years ago revealed, to my surprise, that Water Shrews and Water Voles figured among the prey items of that particular Barn Owl pair (along with larger numbers of voles, shrews and mice).

Pellet dissections make for a fascinating insight into the lives of these charismatic birds and a great educational opportunity. If readers of this blog have ready access to a supply of Barn Owl pellets and would like to donate some, I would be happy to put you in touch with The Cranedale Centre, which regularly undertakes sessions in pellet dissections with young people from Junior age to sixth-formers and I’m sure would be only too happy to feed back any interesting results.

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