November 22, 2015

The owl service

One of the highlights of my two weeks in Northumberland was a trip to Woodhouses Bastle with one of the National Park rangers, Mark. Defended farm buildings dating back to the closing years of the time of the Border Reivers, bastle houses were something I really wanted to research while I was there, for a piece of writing I'm working on, and this was a beautiful example: intact and re-roofed, with a curving internal staircase (not original) thatched deeply by jackdaws with twigs and an upper window with an intimately domestic stone sink in the sill. And there were two barn owl boxes, installed by the National Park and clearly in recent use: the upper, flagged floor was thick with owl pellets, and I pocketed one, and some barn owl feathers, for two London children I know.

Today I visited them, and we dissected the pellet. It was dry and light, the size of a thumb, dark grey with a smooth exterior. In a bowl of warm water it floated briefly, then absorbed the water, sank and began to fall apart.

I'd arrived with tweezers, two identification books (Nick Baker's Nature Trackers Handbook and my childhood favourite, Animal Tracks and Signs) and a magnifying glass. But we swiftly got hands-on, dipping into the water for bones and pulling apart the hanks of dark, wet fur with our hands.

We immediately began finding skulls in the matted fur: soft and impossibly delicate. We eventually recovered four; their orbits almost entirely intact, it was clear the owl had swallowed its prey intact:

Field voles are barn owls' most usual prey, and the shape is right on three of the skulls we found in the pellet; I do wonder if the smaller one here might belong to a wood mouse, though – or perhaps just a juvenile?

We recovered a huge number of bones from the soupy, furry water: the lower jaws with their tiny molars, scapulas, tibias and fibias, humerus, vertebra, radius and ulna – even tiny, impossibly delicate ribs. The biggest surprise was a tiny snail shell, probably eaten by accident as the owl scooped up voles from long grass. No doubt there were microscopic foot bones in there, too, but we weren't aiming at 100% recovery. We took out as many bones as we felt inclined to, and left the rest.

When fully dry, in a day or two, the bones will be paler than they look in this photo. The next (optional) stage will be to fully clean them. Right now they have a coating of animal fat, a substance I could feel on my skin when I washed my hands; biological laundry liquid can help dissolve it, though with bones this tiny and delicate it's a risky process – the enzymes can dissolve the bone itself if left too long. After that they can be bleached using dilute peroxide, like the 3% solution used for cleaning contact lenses. But we might just leave them as they are.

I'll visit again and claim back one skull for my collection (I have one full and one partial fox skull, and a rat, all of which I recovered myself; two sheep skulls, a sheep spine and a pony vertebra, all found; and a crow's skull given to me as a present). But for me the value was in the exercise itself: the way it allowed us a window into the past, and into an unimaginable world. Out there, in the dark landscape, while I was sleeping, or cooking, or watching TV, a Northumbrian barn owl was hunting on silent wings: bringing death to the tussocky fields, and life to its chicks in the bastle house, as safe there now as the family who retreated behind its stout walls from the Border Reivers, four hundred years ago.