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[This is a slightly different version of the paper from that in the printed Newsletter. Ed]

Barn Owls Tyto alba

by Michael Thompson

In 1997 the Pickering Branch of the Hawk and Owl Trust held an exhibition and work shop at Lady Lumley’s School, Pickering. Not only did they exhibit the work of the Trust, but also gave an opportunity for individuals, particularly children, to dissect owl pellets and find out what the birds ate. I went along to the exhibition representing the Yorkshire Wildlife Trust. Amongst the leaflets available was one on how to make a barn owl nesting box, designed by Ted Darlington and Pawl Willett, the latter who is a Ranger with Forest Enterprise. I took one, thinking, somehow, I could make use of it.

Known as the Pickering Box, my next door neighbour, Adrian Thackray, a professional carpenter, made one for me from off-cuts and this was duly erected in one of the tall ash trees at the bottom of our meadow. Initially, the box was used by wood pigeons over two springs, but on 7th July this year my wife, Pat, and I became aware that barn owls had taken up residence. An adult bird, on that evening, was seen entering the box. On the following evening, an adult bird emerged from the box, stretched on a perch provided and then flew off silently towards our neighbouring fields, its ghost-like shape disappearing into the distance. We cautiously approached the box and from it we could hear quiet squeaking noises, indicating that there were young present. Pawl Willett was immediately notified. A week later both parents were returning to the box frequently, often every half an hour, carrying prey items in their talons. In the failing light, I was able to identify voles, and, possibly, large beetles. D.S. Bunn and his co-authors, in a book entitled The Barn Owl (1982), state that the short-tailed or field vole Microtus agrestis and the common shrew Sorex araneus make up the bulk of the barn owl’s diet. However, on one occasion, one of the parents brought in a young brown rat Rattus norvegicus.

On July 17th Paul Willett and Jim Pewtress, along with others, visited the box. Three juveniles were removed from the nest, none of them capable of flight for all of them were covered with pure white down feathers. At this stage of their development, they were too young to sex. All three were of different weights, the oldest being 310 gms., the middle owlet 260 gms. and the still blind runt, which was not expect to survive, only 110 gms. These weight differentials indicate that the female laid one egg every few days. Barn owl clutch size can be anything between one and eleven eggs, peaking at five. An adult bird flew off at the time of this nest box inspection, but by dusk it had returned carrying a vole. It seemed undisturbed by whole procedure.

For the following few weeks I watched the barn owls most evenings at dusk: the larger female, identified by the brown, flecked feathers on her underparts, was bolder than the male, with his white underparts. Almost every evening two chicks could be heard calling, their calls being described as a raucous snore, and could be heard from quite a distance away. Occasionally, a parent bird, on approaching the nest and being aware of my presence, would let out a penetrating scream-like call warning the youngsters. Pawl and Jim returned to inspect the box on 8th August. All three owlets were still alive, and all weighed 380 gms., the runt having caught up with its siblings. The two older birds were developing their secondary feathers and both were males, but the runt, which was still covered with down, was not sexed. Each was ringed (Ring Nos. GM 30828 – 30830). By 28th August, two owlets had emerged from the box and would spend a lot of time flapping their wings, in preparation for flight. By mid-September all three were flying around the ash trees, but still being fed by their parents. Often, as a learning exercise, they would land on our neighbour’s post and rail fence, launch out over his meadow and return to the same perch. The last of the owlets, probably the runt, left the vicinity of the nesting box on 6th October.

So far some 17 Pickering Boxes have been erected in the Vale of Pickering, and the majority, according to Pawl, are being used by barn owls, either as nesting or roosting sites.

The box scheme has increased the number of barn owls in the area. Pawl suspects that our pair were first year breeding barn owls, and that they had reared three chick was a good result. It also indicated that the food chain, on which they are dependent, is in good shape. Nationally, the number of breeding barn owls has increased from an all-time low of 3800 pairs in early 1990s to 4400 pairs in 2000, all mostly due, according to the Hawk and Owl Trust, to the box scheme. Once discovered by our barn owls, there is every reason why they should return again next year. Let’s hope so.

Michael Thompson 5.11.00.

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