Owl Sense Page 3
In spindrift mist a white owl sits
on the barn’s storm-wrecked hull.
Moon-faced she takes the last midnight watch,
talon-tight on the listing deck of oak.
In place of the nest, a squared-up show boat,
no space for quilted flight,
no cobwebbed corners,
no mothy, fathomless dark.
JENNIFER HUNT ‘Barn Conversion’
We have a long entanglement with this species, tethered by a story more complex than our simple admiration for its beauty, its super-senses and its formidable hunting skills. Our association is important for the owl, too. It has adapted to live alongside, even among us. Our closeness has developed over time, like a marriage, but perhaps not an altogether happy one.
As a vole hunter the Barn Owl was attracted to the dense rodent populations that inhabit our man-made rough pastures and meadows. But while in the early twentieth century this owl was a common sight in the fields of lowland Britain, it is no longer the case. The Barn Owl Trust tell us that the causes of the owl’s current decline are the result of human activity: changes in agriculture, loss of nesting and roosting sites, the increased use of lethal hazards such as rodenticide, and the proliferation of trunk roads all have combined to impact on the sensitive Barn Owl. It is likely that there are fewer than 5,000 pairs left in Britain.
To begin at the beginning. These raptors were on the planet long before us. Fossil remains of owls have been dated from 65 to 56 million years ago. In the Pleistocene, Ornimegalonyx, giant Barn Owls, ranged across the Mediterranean area. They stood over a metre in height, weighed twice the heft of today’s Eagle Owl, and preyed on large rodents such as capybara. Our human ancestors may have noticed these hunters, and been fascinated by their nocturnal powers and haunting cries; unable to explain the owl’s uncanny skills without the benefit of science, they might have believed these creatures were party to some knowledge that eluded us.
The Barn Owl’s long, lightweight wings evolved for grassland hunting, not dense forest like some of the short-winged owls. It came from the plains and scrub of warmer, drier climes. But as the ice sheets retreated from Northern Europe between ten and twenty thousand years ago and humans spread north in greater numbers, so followed this wraith-like owl. It was drawn by the pasture that small-scale farming created, and later found the protective nesting cavities that were offered by some of our cliff-like structures: farm buildings, attics and haylofts, churches and homesteads all mimicked the owl’s native cliff-scapes and provided the perfect place to breed. So from our early history Homo sapiens and Tyto alba began to share both feeding grounds and housing. While some of the owl’s northerly movement may have been due to climate and habitat change, much of this was human-made. The owls came to depend on our shared habitat where it could easily find shelter: drifting low above scrub and floating over meadow grasses, it uses its acute hearing to hunt in prey-rich portions of grassland, its super-sensitive ears pinpointing small rodents with ease even in the faintest glimmer of moonlight.
Our lightly grazed pasture was thick with native grasses perfect for the tunnels and nests of small rodents, particularly field voles, the owl’s main food source. For over a thousand years our clearings, meadows and summer pastures have made a dense and diverse thatch – velvet grass, sweet vernal-grass, false oat-grass, red fescue, rough meadow-grass, smooth meadow-grass, Yorkshire fog, false-brome, wood false-brome, upright brome and cocksfoot – all useful species that when left un-mown or un-grazed decompose so slowly that they form a ‘litter layer’ providing protection for small mammals. Fields with such ecological niches were perfect foraging ground for the owls, but this once-common farmland is under threat – from increasingly intense agriculture, mechanised farming, and more aggressive use of rodenticides and pesticides.
But it is not all bad news. The agricultural relationship between humans and Barn Owls has taken on a new aspect in recent years. It is accepted that the Barn Owl actively removes vermin; but could Barn Owls remove as many if not more rodents from our fields and barns than a chemical intervention? To address this question and raise sympathy for the Barn Owl, in 2011 Mark Browning dreamt up the Barn Owl/Rodent project. This flash of inspiration was set up in California to investigate whether it was more sustainable to deal with an infestation of rodents by owl or by rat poison. A 100-acre vineyard had been overrun by a voracious American rodent named the pocket gopher. These prolific nibblers were causing huge economic damage to valuable vines. For the project, Browning designed owl nest boxes and placed them at 500-metre intervals along the perimeter of one vineyard. By the following year, 25 Barn Owl nest boxes had been erected and these had attracted 18 pairs of Barn Owls that fledged 66 young. Browning calculated that if each adult owl needed one rodent per day and the growing young double that, a conservative estimate was that in 2011 the owls consumed 9,576 rodents in total. In 2012, the growing population of owls consumed approximately 15,204 rodents: by any account, a prodigious number of rodents was being eliminated. The owls were shown to be targeting the vineyard where the gophers burrowed, and the level of gopher damage was considerably reduced.
Even with the initial investment, the owls would pay for themselves within two to five years: for the Californian study the original cost of twenty-five nest boxes, poles, mulch for bedding, and installation labour was approximately $6,000. By the end of the second year, the rodents harvested by the owls came in at a cost of $0.24 per rodent. And as the study rolled on, the cost per rodent declined year on year until, after a five-year period, it was all but negligible.
In contrast, some landowners use strychnine pellets to control their rodent infestations. Strychnine costs hundreds of dollars per application, and the process is lengthy and time-consuming, requiring days of labour – only for the whole process to be repeated once the rodent population recovers. Who could argue: the Barn Owl was the victor!
In Jordan and Israel similar Barn Owl projects have taken place, and the owl is now celebrated for its uses in terms of farming sustainability. In such pioneering conservation schemes these useful raptors are replacing pesticides.
Coupled with the loss of its traditional habitats, here in Britain the Barn Owl is on the northernmost edge of its range. In the highlands and far north it is too cold, too wet and too blowy to be comfortable for the delicate, warmth-loving Barn Owl. Its plumage is not waterproof and with no oily defence against heavy rain, if it becomes waterlogged it cannot fly. If it cannot hunt, it may quickly starve or die of exposure. Frost and frozen ground in winter, heavy rains in autumn; flooding, high wind; all extreme and unpredictable weather threatens the ability of the Barn Owl to feed. As a lightweight bird it has so little body fat that it needs the warmth and shelter of beams, the insulating thatch of our old barns. But recent bad winters have made it increasingly difficult to find food; rain makes it impossible to hunt, snow and ice send prey scurrying underground or affect vole populations so severely that the owls have simply starved. As a vole specialist the Barn Owl is especially vulnerable, its prey subject to huge fluctuations. It is also extremely site-faithful and so doesn’t have the option of simply abandoning a site that is no longer hospitable. A home bird, almost without exception it remains in its own patch all its adult life and nests consistently in the same place. It does not migrate, and may only vary its roosts occasionally. Many generations of Barn Owls might stick to the same site. Amongst unsympathetic conversion of its sheltering roosts, loss of mature trees, and ever-more intensive farming, along with encroaching roads and faster-moving traffic, the Barn Owl is not well-adapted for survival.
*
In March I’d started to find owl pellets. Between the size of a conker and a champagne cork, these undigested, regurgitated remains had been cast along with whitewash splatters beneath the old oak near my home. These were signs that indicated only one thing: the presence of an owl. As the days lengthened, my interest deepened. Barn Owls begin to pair up in late winter and might
settle on a roost that will be a good potential nesting site. In the privacy of their nest cavity or a hidden roost high within the beams of an old barn there will be much courtship bonding. All through the spring, mutual face-preening and cheek-rubbing are interspersed with the male bringing the female gifts of voles. If they can get into breeding condition and the food supply is good, around 75 per cent can breed any time between March and August, but eggs have been found in January, and it is possible that if the owls are in the right condition they could breed at any time in a good year. If it is a bad year, and their habitat does not provide enough voles, mice or shrews, breeding is more likely to fail, or even not take place at all.
I watched the roost. Sometimes in the tree an alert whiteness was perched, watchful, occasionally uttering nervous calls. Around the same time as my owl-watching, out of the bedrock of our home a series of tremors happened. One of our own young got sick. It was an illness that was so unusual, so difficult to diagnose and then to treat, that its unfolding had a seismic effect on us. Perhaps illness is always like this, from the common cold to cancer, all of them jostling somewhere on a Richter scale of life change. It was around April when we noticed the first signs. My nineteen-year-old Benji and I were sitting by the river, where the crepuscular soundscape of bird chorus was heightening over the marsh. For Benji, on the cusp of moving into the adult world, this was time off before his final year in college where he was learning to design and build houses. I relished his quirky end-of-teenage company sitting next to me, close and content. I knew that there would not be much more of this. Soon he might be away at university and things would never be quite the same. When he tipped awkwardly sideways, shivered for a few moments, and slowly righted himself, I thought nothing of it. He was quiet for a moment and then he said: ‘Do you ever get that thing where you start twitching?’ I turned to look at him, puzzled.
We didn’t know it, but somewhere in the invisible pathways of Benji’s brain, some synapse was misfiring. Amongst the millions of neurons inside his head, messages were going awry between nerve and nerve, from pathway to pathway.
We would often come down to the reed beds like this to hear the owls. It’s hard to write this in hindsight and accept that, at that point, we had no idea of what was to come for Benji. At that moment, our attention was all on one owl, and now it was calling across the reeds to another: a screech, then a reply, as if they were throwing lightning bolts to one another, as if each was catching the other’s cry in its craw and lobbing it back.
‘Look,’ Benji said, feeling better again. He touched my arm and we watched a white owl lift free of the reeds and emerge to glide across the river. Its body was reflected in the caught light of the water.
*
In May and early June I always left our window wide open to catch the height of the dawn chorus. Some nights, and very early mornings, I was woken by the owl’s disembodied cry, a shriek that jangled the nerves. It reached right into that place where once long ago we might have shivered at the ill omen. The cry would draw me out of my bed, and dawn walks down the green lane, through the gap and into the field, had become ritual. Each time, it would take a while for my senses to attune. Shadowy leaves, roots and earth, uncanny darknesses, the strata of animal habitations, weasel runs, vole ways. Leaves dripped, bird wings flickered. Usually, Benji was safely asleep and his younger sister Jenny tucked away in her world too.
The cry, when it came one morning, was so piercing that I leapt out of bed and scrambled for my binoculars. Leaning out in the half-lit air I caught the mothy wings, the buoyant turn as the sensitive ears captured every minute sound: the twitch of insect legs, the drone of power lines, the rasp of fescue stems. The feathered radar of its face tilted to block out interference, to capture the wisp of light paws: prey – right there. Wings folded so they were streamline-smooth, talons outstretched, silently it dropped.
I leant further out of the window. The field curved over the horizon, and I could just make out not one but two shapes moving. My owls were a pair, their long, light wings carrying them over swathes of grass. The screech of the male ripped the air again and seemed to be answered by the female. The scratchy calls had been pressing into my inner ear for weeks and now their urgent voices simmered, fingernails on sandpaper.
When the owl is hunting, it quarters the field, back and forth, and a strike may grasp nothing. Only a small percentage of attempts end with a kill and this means that Barn Owls live on a knife-edge. This is a predator that has to be light enough to drift silently over tall grass, long-winged and elfin enough to float, then to dive in and grasp what might be hiding there. As well-evolved for the task as it may seem, there are stiff challenges: it has a ‘low wing loading’ that means it is so light it can glide buoyantly and effortlessly, but Barn Owls have a body mass index so precarious that if they do not make a kill for more than a few days they can quickly starve.
I skipped a shower and dressed in a vest, jumper, long trousers and socks. It could be cold and damp in the fields this early; I pulled on wellington boots and left my husband Rick, just woken, his face blue-lit as he blearily tapped at the screen of his iPhone. I trotted out, refreshed by the washed air, the blue sky filled with a yawn of plane-sound. Towards the field, along the edge of suburbia, prickles, ferns and nettles lined the way. Then the sign, sprouting up: ‘Site Acquired for Development’. The announcement of ‘stunning new homes’ had been there for a week or so, jutting out of the hedge and into my thoughts. I wanted to pace out this place, to watch over it a little. This rough-edged bit of land housed dwellers far more sensitive than its new owners would see.
In the hedge, thick, sappy Spanish bluebells had broken out of the nearby gardens on the edge of town and taken over sunny parts of the banks. They were going over now, and pale; some were swollen with seeds. Just as my head was down in the flowers and seed heads something flickered on the edge of my vision. That sylph-quiet movement of wings.
It quartered the field, this way and that, catching the light. It came again, swivelled, saw me and veered off. I took a few steps forward, keeping my silhouette within the shade of the hedge. And then it stooped, diving down on to something.
Brief sightings like this reveal fleeting glimpses of these creatures, so I tried to listen harder, engage all my senses, walk more softly; to close in without encroaching. I waited for the cry but none came, so I spun my binocular focus to where it dropped into the grass: and there it was, rising up, weighted with prey. The close-up visual framed chunks of the bird as it flew. I held my breath at its smooth white breast. No speckles. It could have been the male? Where was it taking its catch? When it hovered briefly the perfect fan of tail feathers shone and light fell through its wing tips.
An adult Barn Owl can swallow a whole field vole in one go. Owls cannot chew, so within a few minutes the prey is crushed and dissolved in the bird’s ventriculus, or stomach. Once the fluid and soft tissue in the vole’s body have been liquefied, the fur and harder parts pass into the gizzard. This muscular stomach is an organ that birds have instead of teeth. It retains the indigestible bits – the bones, teeth, claws and fur – crushing them into a compact, gizzard-shaped pellet. The pellet will remain there for a period of hours until it is regurgitated and dropped to the ground. It is very tempting if you find one to take it home and try to identify what the mystery parts are. Fur and bone dissected with tweezers under a lamp through a hand lens become field vole jaws with incisors and molars. The species of vole or mouse is indicated by the colour of the molars: are they pinkish? Or rotated? There might be meadow pipit feathers, rat skulls, each pellet a map containing all the grizzled drama of the owl’s nocturnal predation. And the Barn Owl breaks the rules. When it is under pressure from breeding and needs to catch more voles, or if it is unsuccessful in the night, it often hunts in the day, preying on different species, but primarily here in the UK on the variety of small mammals that inhabit our grasslands.
It began to rain softly and seeing the apex of a barn ro
of and an ivy-clad gable end I scuttled into the lee for shelter. The barn was half-ruined. When I got further inside, something alive was there, a presence beyond any mice or jackdaws. I stepped further in, my feet grating on the dusty floor, and the quiet was broken by a rattlesnake hiss. It bubbled up from nowhere in particular, making my skin prickle. Hunched in a corner, a small, downy face and two dark eyes stared at me.
A fallen owlet.
And higher up, the source of the hissing; a small snowdrift of siblings, calling from their high ledge. I had thought the owls might nest in a cavity in the old tree, but of course they preferred this rickety but reliably dry human-made space instead.
How quick we are, to want to come to the aid of fallen things. This tumbled chick wouldn’t last a night on the floor while the foxes had cubs to feed.
It’s so easy to be preoccupied with the guilt of it all: climate chaos, the loss of species, the Pacific Garbage Patch. Here was something to save. I had heard news that the owls were in trouble that year. While we suffered our own weather patterns, outdoors the other tribe, who still have to live on their skills and their wits, who take their chances and don’t always make it, had survived all through that stormy, wet winter. They had survived well enough to produce young.
I scanned the wall for handholds. I could try to climb up and put it back and then quietly withdraw, hoping the parents would soon return. So I approached, and the owlet wobbled, but it didn’t flee. I placed my hands around its warm, tickly body. I checked the thinly muscled wings. Some of the adult feather shafts had begun to come through, encasing what might one day be flight feathers if it survived the summer. Before it reached maturity its extravagant body-warmer of soft, white down would insulate its back, head and belly. It was way too small to fly yet. How old? Three weeks, perhaps four?
Its feet wriggled at first, but soon its feather-weight settled to my grip. I expected it to smell like a kitten but its alien stink of rotting mouse, vole blood and acrid ammonia hurt my nose. There was something part-reptile there: I looked into its wincing face, felt its scaly feet, and at their tips, whetstone-grey talons, already gripping fiercely. Millions of years of evolution, honed for predation.