As a retrospective update on my barn owl box experiment this year, I was keen to find out what (if anything) the birds had achieved during their period of enthusiastic activity in May and June. Having solemnly resisted the temptation to look too closely at the nest box for fear of disturbing the occupants, I recently set up my trail camera nearby to see whether or not the nest was still “active”. Ten days went by, and the only activity at the box was a visit from a single pigeon. From this I assumed that the coast was clear and went in for a closer look. Sure enough, a thick cobweb across the doorway added further proof that nobody was home.
Peering in through the door, I found that the box was carpeted with a deep bed of dead voles. Mounds of corpses lay strewn in a mat almost three inches deep, and many of these had been mummified, frozen forever in a dry, twisted rictus – little yellow gnawing teeth bared like Egyptian mummies. In the far corner of the box were two small, white, almost spherical eggs. I came away from the box quite confused. Reading through my books on barn owls, I found that barn owls can lay large clutches and eggs, and one or two often don’t hatch. Of course it’s possible that these owls reared a large brood of healthy owlets and the two eggs were simply the leftovers, but I couldn’t reconcile the thought of large, mucky, scuffling chicks crowded together in a small space for an extended period without leaving a single mark on the pure, silky white eggs.
It seemed more likely that the nest had been abandoned after only two eggs were laid, but judging from the vast surplus of food which had been gathered and wasted on the floor of the box, it was hard to see hunger as a cause. I can’t ignore the possibility that disturbance might have played a part, since this is a functioning agricultural shed which can see lots of activity during the summer months. To some extent this is unavoidable, but there must be a compromise to tip the scales in their favour. The old shed which stood on this spot played host to generations of owls which bred successfully for decades, and this space was no more noisy or disturbing than the new. I’m confident that the box is in a suitable spot, but if disturbance did play a part, we must take extra care next year to tread more carefully and be more aware.
In the meantime, there has been at least one barn owl around the house all summer, and I am sufficiently enthused by my first attempt with owl boxes to build a second. I can see an excellent spot for a box at the far end of the yard where there will be very little human disturbance, and I will simply need to open up an old lunkey to allow the birds access through the gable end.
I can’t help feeling a little uncomfortable with the idea of bird boxes; the concept smacks of “wildlife gardening” and typically human micro-management. I would much rather be managing rough grassland habitats than prissily building custom “homes” for wildlife, but it really does seem like an availability of nesting sites is a genuine limiting factor in barn owl populations. If we can draw in a pair to breed in the yard, I can focus on creating a mixture of habitats to boost the voles and mice in the fields.