The secret life of owls

Strong, silent and instantly recognisable, the birds of prey are perfectly tuned hunting machines. And the long winter nights are the time to watch for them

By John Lewis-Stempel

The dictionary definition of an owl is “a nocturnal bird of prey”. Not absolutely all owls, however, are night birds; up on the black Welsh hills beyond our house, the short-eared owls regularly quarter (range up and down) the stunted, wind-whipped grass in broad daylight. Then there is the matter of size: the elf owl is Lilliputian and barely dents the scales at 47g, while Blakiston’s fish owl is Brobdingnagian and nearly breaks them at 4,500g.

There are white owls and brown owls. Owls that live on fish, owls that eat insects. Across the world there are currently around 225 different species of owl.

Owls are instantly recognisable. They have a big, domed head, a flat face, large forward-facing eyes and a hooked beak for tearing flesh.

They have understated plumage, invariably brownish, and evolved (or designed) to allow each species to blend into its chosen habitat. While the majority of owls are tenants of the wood and the forest, they can also be found on terrains as opposite as Arctic tundra and African desert.

Under attack

Curiously, the predacious owl chiefly requires camouflage to roost in peace. Owls are feared by other birds, and if spotted in daytime are attacked by even the tiniest passing passerine.

When “mobbing”, antagonistic birds will dive-bomb the owl, claws extended, descending to within an inch of the owl’s face. Such is the compulsion for other birds to mob owls they will attack stuffed specimens, even wooden facsimiles. The owly silhouette is as distinctive to a bird as it is to us.

Over the millennia, humans have taken advantage of the mobbed owl to fill the stew pot. A Greek amphora from the sixth century BC shows an owl tethered to a post; a flock of birds has landed on an adjacent tree, the branches of which have been smeared with adhesive “birdlime” to trap them.

Two centuries later, in about 350BC, Aristotle recorded the use of the owl as bait: “In the daytime all the other little birds flutter round the owl – a practice which is popularly termed ‘admiring him’ – buffet him, and pluck out his feathers; in consequence of this habit, bird-catchers use the owl as a decoy for catching little birds of all kinds.”

An identical technique is depicted in the De Lisle Psalter of England, about 1310, where birds landing on a branch to mob a tethered owl get trapped by birdlime. The cockney rhyming slang “doing bird”, meaning time spent in prison, comes from “birdlime” via “doing time”.

Night vision

Can owls see in the dark? Nearly. When it is rat-black, the iris of an owl’s eye opens almost completely to allow in all the light there is. Also, the retina is crammed with rods, the receptors concerned with seeing in poor light conditions. As a result, a long-eared owl can see a mouse in a light level equivalent to one candle in a football stadium.

With this light-sensitive optical equipment Old Brown, as Beatrix Potter called the tawny owl in The Tale of Squirrel Nutkin, can fly around his familiar wood at night, although not under leaf canopy when it is wholly overcast. Fortunately, for tawnies and other night owls, there is always the subfusc of dawn and dusk.

Owls have the best “stereoscopic” vision of all the birds. An owl’s eyes almost fill its skull, taking up to 70 per cent of the available space. A tawny has a skull the size of a golf ball, but eyes the size of a human child’s. By having its eyes pointing forward, the owl is killer-efficient in determining distance and movement. But there is a drawback to the owl’s supersized eyes: they are immovable in the skull. An owl cannot roll its eyes, for example. When owls need to judge the position of an object they bob, or swivel, their heads about.

Bird watching

There are times and seasons to watch for owls. That half-light at the beginning and the end of the day offers the best opportunity for watching, as opposed to merely hearing, the nocturnal owls, particularly in bitter winter weather when birds invariably extend their hunting time beyond darkness.

Early winter is the prime time to hear tawnies, when they are staking their claim to territory. Follow the sound trail through the frosted air, perhaps for a mile or more. The length of the winter night means that the owl will call on and off for over 12 hours, and well past dawn.

Despite their deadly keen eyesight, owls can bungle the identification of stationary objects.

When I was a teenager, I was standing watching a barn owl quarter the harvest field on a late and breathless July evening. The bird flew so low that its trailing legs skimmed the ears of wheat. It progressed as methodically up and down the field as Mike Hughes, the ploughman, had four months before. Then the owl veered to rest on the convenient post, which was me. Only when I shrieked did the owl swerve away, her witchy claws catching my hair as she did so. We were both equally surprised by the close encounter.

When the eyes are not enough, such as on a moonless autumn with the leaves still clinging to the trees, owls locate their prey by listening for movement. In owls, the ears are set asymmetrically in their skulls, with one ear as much as 15 degrees further up the skull than the other, and sometimes of larger size. This means that each ear receives sound at a slightly different volume and angle, which allows the owl to pinpoint where the sound comes from.
Some nocturnal owls can kill by hearing alone. In total darkness. In blackout. Night is no friend to prey animals when an owl is about.

Silent wings

The owl on the hunt, having located its prey, continues to listen throughout the approach, which is done on silent wings, partly to avert the alerting of prey, partly because loud wings would interfere with the bird’s own hearing. The victim only becomes aware of the owl’s presence as the talons close in deadly grip. Owls are the avian stealth predators.

They have special feathers to facilitate silent flight. Comb-like serrations on the leading edge of the wings and a velvety fringe on the trailing edge “dampen” noise. Then there is the overall softness of the plumage; an owl in the hand is curiously fluffy. The multitude of downy feathers make the owl look a lot larger than it really is; a long-eared owl has a 95cm wingspan but weighs the same as an orange.

The feathers grow down to the razor-slash claws, to protect the legs from bite-back prey (barn owls have been known to attack stoats, a foot-length of pure violence if ever there was one). Feathered legs also minimize heat loss, crucial to those wait-on-the-bough owl species, like tawnies, which lurk immobile for long periods waiting for prey to happen along.

The talons, on which two claws point forwards and two back, are the owl’s primary weapons. They capture and kill the bird’s prey. Prey is taken by the bird swooping from a perch, or from low quartering flight, between 0.5 and 2m above the ground. The momentum of the pounce or swoop adds to the weight of the owl and enables it to kill animals twice its size. In all instances the prey is struck with the feet pushed out in front of the bird, the talons fully open, to make a spring trap of claws. As the owl’s talons slice in, then close, the prey dies from shock or the puncturing of a vital organ.

The evolution of the owl reaches its apogee in this moment: a perfect connect between targeting ear/eye and the striking talon. If the prey is still somehow alive, a swift sharp nip from the owl’s hooked bill will finish it off. Owls are purist killers. Some avian predators, such as the peregrine, taunt their victims. In the battle of survival, the owl eschews posing for economy and efficiency. They kill. Fly on. Kill. Fly on.

Owls and humans

This is not to say that owls are without gentleness, though this is expressed to their kin, and those humans who adopt the birds. Owls make good pets. Florence Nightingale rescued an owlet from the Parthenon after it fell from its nest. She named the bird, a little owl, Athena and kept her as a companion.

Athena would perch on her mistress’s finger for feeds, as well as bow and curtsy on a table, and lived in Nightingale’s pocket. When the beloved Athena died in 1855 Nightingale delayed her departure for nursing duties in the Crimea so she could arrange for the bird to be expertly embalmed. It is currently an exhibit at the Florence Nightingale Museum, London.

Pablo Picasso also kept a pet little owl, which lived with him in his studio in Paris. According to Françoise Gilot, Picasso’s muse and lover, the owl “smelled awful and ate nothing but mice. Since Pablo’s atelier was overrun with them, I set several traps. Whenever I caught one, I brought it to the owl. As long as I was in the kitchen, he ignored the mouse and me. He saw perfectly well in the daytime, of course, in spite of the popular legend about owls, but he apparently preferred to remain aloof. As soon as I left the kitchen, even if only for a minute, the mouse disappeared.” Picasso thought of himself as an owl, because of his staring eyes. An owl motif featured in many of his ceramics and paintings, famously, “Owl on a Chair and Sea Urchins” from 1946, and “Cage with Owl”, 1947.

Creatures of the night, owls communicate primarily by sound. Apart, perhaps, from the bassoon “hoos” of the tawny, owls could never be declared musical. Still, as the Danish proverb has it, “If there are no nightingales, one must settle for owls.”

‘The Secret Life of the Owl’ by John Lewis-Stempel (Doubleday, £7.99) is out now