* * *
Owls have very strong legs, with a conventional hip joint at the pelvis and two other major joints (again, a glance at the skeleton drawing on here may be helpful). At the bottom end of the thigh or femur, the upper of these two joints – once, the reptilian ‘knee’ – flexes backwards, like our knee, but we hardly ever see this under the body feathers. The lower joint, at the bottom end of the now fused tibia and fibula bones of what was once a shin, flexes forwards. This was once the reptilian ‘ankle’; but below it the reptilian ‘foot’ has elongated enormously, and fused into what we perceive as the owl’s whole lower leg (the tarso-metatarsus). This terminates in what looks to us as if it should be an ankle, but which is actually more akin to the ball of our foot, though with toes extending from it both forwards and backwards.
Most of the time Mumble’s skirts of body feathers and fluff covered her legs down to the second, forwards-flexing joint, and when she settled into her habitual squatting pose the lower legs disappeared too, leaving only her claws showing. She often perched (and slept) standing on one leg only, with the other folded up ‘into her pocket’ among the body feathers. When your instinctive sense of balance is as good as an owl’s, there is no point in exposing both your feet to the winter weather at the same time, and thus risking them both being cold and stiff if any sudden emergency or opportunity occurs.
Owls have four toes on each foot, and when they are standing or perched at their ease two of these point forwards and two backwards. However, they have a ‘trick’ joint at the base of the outer rear toe that enables them to swing it round towards the front at will, to give a three-forwards/one-backwards grip. They may do this in flight when about to land or to strike at prey. Mumble’s whole legs and the upper surface of her feet were covered with a fur of fine, pale, buff-grey feathers, to keep them warm and to offer slight protection against the nipping teeth of any defiant prey. On the rare occasions when her whole legs were exposed I noticed that the feathers were thicker around her lower legs and feet than her upper legs, giving the impression that she was wearing fur boots laced tight at the top and flaring out over the instep below. Among these foot feathers, sensitive filoplumes gave her nervous system a degree of feedback about anything they touched.
The bottoms of Mumble’s toes showed pale pinkish-grey skin covered with close-set nodules, and this nubbly ‘shagreen’ surface gave her a secure grip. The talons emerged from high up in big ‘knuckle’ pads at the ends of her toes. They were glossy dark grey growing from a straw-coloured base, about three-quarters of an inch long (20mm-plus), curved like sabres and needle-pointed. When Mumble stood on a flat surface the upwards curve of the claws from their base in the pads kept all but the points off the ground. When she closed one foot to ‘put it in her pocket’, or both of them in sustained flight, the front and rear talons folded from the knuckle pads right inwards under the toes, like the opposed blades of a jack-knife closing beside one another. I learned that the inner front and rear toes (which do the primary gripping, like our forefinger and thumb) were controlled by a sort of ratchet that allows owls to maintain a crushing grip without consciously exerting constant muscular effort – the grip that enables them to kill their prey almost instantly.
* * *
I badly wanted to examine Mumble’s wings in detail, but – naturally – she refused to tolerate any handling of these delicate miracles of engineering. Her short flights, and her stretches during grooming, were too brief for me to note the details properly, so I had to resort to studying published illustrations, later comparing these with her moulted feathers.
Another glance at the skeleton drawing on here will show how the wing has evolved from the original reptilian ‘arm’ or front leg. From the shoulder joint outwards, it now has three sections that appear to us to be of roughly equal length, though the length of the outer section is almost entirely made up of feathers. The single ‘upper arm’ bone or humerus ends in an ‘elbow’; from this joint the double ‘lower arm’ bones, the ulna and radius, flex forwards, ending in a ‘wrist’; and from that the partly fused and elongated ‘fingers’, the carpo-metacarpus, flex backwards. (Both the shoulder and the ‘elbow’ joints are invisible to us, hidden by the thick feathers covering the structure.)
Since tawnies are woodland owls, who have to be manoeuvrable to make agile banks and turns during flights between close-set trees, their wings are relatively shorter and broader than those of owls that make more extended flights in the open, like the Barn and Short-Eared. However, for a grown female the wingspan still measures more than a yard, with distinctly separated feathers at the tips. From the tip inwards to about the mid-point of the trailing edge, each of Mumble’s wings was furnished with ten of these large, strong pinions or primary flight feathers. From the mid-point inwards to the body, the trailing edge continued in a similar row of anything between eleven and nineteen smaller secondaries (some sources describe the smallest of these feathers, closest to the body, as tertiaries).
On the leading edges of her wings, about one-third of the way in from the tip and immediately outside her ‘wrists’, she had separate, outwards-pointing alula feathers, growing from the vestigial ‘thumb’ of the reptilian ‘hand’ that had evolved into the outer one-third of the wing. This bone could be manipulated independently, so the feathers acted like the leading-edge flaps on aircraft wings. (Though in fact, of course, the correct way to describe the resemblance is that the aircraft’s flap acts like a very crude and clumsy imitation of the alula.)
Most birds – and some owls – have stiff, glossy flight feathers (remiges, oars) that cut through the air like knives, but Tawny Owls are among those species that have adapted to sacrifice sheer speed in return for almost noiseless flight. The individual barbules along the leading edges of their primary feathers are not ‘zipped together’ but free, forming a fine comb or fringe. This fringed effect, and a velvety pile over the surface of the feathers, breaks up the turbulence of the air passing over the wings, and thus reduces its rushing sound to almost nothing. Coupled with the low wing-loading that makes constant flapping unnecessary, this gives the owl the gliding, virtually silent flight that is so invaluable when hunting. There is no noise of beating wings to warn its prey, nor to interfere with the incoming higher-frequency sound signals being processed by its sophisticated ear-and-brain computer.
On the top surface of Mumble’s wings the background colour of the primaries and secondaries ranged from mid-brown through pale brown to off-white at the trailing edge and tip, and each was barred across with five or six irregular dark brown stripes. From the leading edge of the inner part of the wing a series of overlapping rows of velvety brown covert feathers, increasing in size from front to back, ‘faired in’ the bases of the secondaries and primaries. The undersurfaces showed the same basic camouflage pattern as the top, but paler, as if misted over with a spray of pale greyish-cream colour.
Mumble usually only opened out the three sections of her wings to full spread when she was either flying or giving them a thorough stretch. The rest of the time she kept the outer two-thirds – from the ‘elbow’ forwards to the ‘wrist’, and from the ‘wrist’ backwards to the ‘fingertips’ – folded up together in a tight inverted V-shape, with the primaries closing underneath the secondaries. From its normal position in repose the thick, smoothly feathered apex of this V looked to human eyes like a shoulder, but it was in fact the bent ‘wrist’, held pressed against the side of her invisible shoulder joint. Most of the time she kept what had been the reptilian ‘upper arm’, between shoulder and ‘elbow’, pressed back tightly against her side; she only partially extended it in order to move the two outer sections around as a single thick, closed fan of featherwork.
* * *
While Mumble was patrolling around the living-room floor one evening, her vainglorious strut suddenly reminded me of a character in a Japanese samurai film. Like some warrior played by Toshiro Mifune, she had the touchy air of someone who is ready, at an instant, to ta
ke furious offence over some imagined slight. She carried her head up and back with her ‘chin’ tucked in, and darted jerky little glances in all directions; once the fancy struck me, I could almost see a tense hand resting on a pair of sword-hilts.
This conceit was followed immediately by another – that her feathers actually had something in common with a sixteenth-century samurai’s lamellar armour. In both cases, many small individual elements – for the samurai, laced-together iron strips, and for Mumble, individual feathers – appeared to be assembled into a series of separate larger panels. Like some wealthy daimyo’s lacquered, silk-laced composite cuirass, they were intricately barred and powdered with the subtlest of colours. During her first couple of months, when she had still been wearing what looked like a one-piece Babygro of woolly down, this had seemed to move – if at all – like a single surface. Once she began to come into feather, however, her selective control of her plumage became fascinating to watch.
By muscular action under her skin, Mumble could not only clench or splay the feathers on various parts of her body at will, she could also move whole groups or ‘armour panels’ around independently of other groups. When she ducked to grab at a feather low on the left or right side of her belly and preened it upwards, then that whole half of her front was lifted out of shape in a single mat, while the other side remained flat. This ‘panelled’ effect was very noticeable in the shawl of scapular feathers at the top of her back, which overlaid the rear edges of her folded wings. This shawl usually looked like a single assembly, but occasionally I would see her separating it into left and right halves. She could shrug it far round to either side for preening, and it opened up and lifted out of the way as she spread her wings. When she folded them again, the shawl was puffed out and half extended until the wings were furled tightly against her body under it. Then she gave a little wriggling shake as she dropped it and closed it over the joins, fairing everything smoothly into a single, apparently continuous surface.
On these and many other occasions, it struck me that my flatmate was not simply beautiful; she was a supremely elegant example of functional natural design.
7
Mumble’s Day
THE MOST IMPORTANT daily milestones in Mumble’s routine were naturally the simple necessities of life: feeding, digesting the bits that were nutritious, evacuating the waste products that weren’t, and grooming herself to keep her feathers in perfect order. Any waking time left over from these essential tasks was spent in keeping a beady eye on her surroundings, and – particularly in her younger years – in playing ‘war-games’.
* * *
Ever since she arrived in the flat she had been able to swallow a chick whole, so I could forget the repellent task of scissoring them in half that I had had to perform for Wellington. Since a rough estimate of her body weight suggested that she needed about 4 ounces of food daily, the basic ration pack was two chicks. (This was not invariable, because even the European Union has not yet enforced regulations demanding that chicks come in perfectly standard sizes.) Usually I fed her these last thing at night, but later I slipped into the habit of dividing them between supper and breakfast. My notebooks don’t explain this; it may have been her idea, but I suspect that it was so that I had a means of tempting her to get into the basket for transit to the balcony cage on the mornings when I had a commuter train to catch and she was playing hard to get. (At the time I never gave any further thought to this, but much later I realized that I must have been duplicating the time she spent on digestion each day. Luckily this seemed to do her no harm, since she sometimes simply chose to leave part of a chick on one side as a snack for later; but it played hell with my already doomed attempts to calculate when – and therefore where – she would defecate.)
On our first few nights together I had tossed the suppertime ration into her kitchen cage as a way of luring her in there for the nightly lock-up, but this very quickly became unnecessary. As soon as I whistled, or took thawed chicks out of the fridge and dunked them in hot water to take the chill off, she flew straight into the cage and sat impatiently waiting for me to serve them up, often with a little chitter of eagerness. If I offered a breakfast chick when she was already in the balcony cage, she leaned forwards so impatiently and so far that she had to spread and flap her wings for balance, half hovering at an angle of 45 degrees but with her feet still clutching the perch. In this gargoyle posture, she snatched the chick with her beak, making metallic chitterings with her mouth full as she wound her body back through the air to a stable base. Then she transferred the chick to one foot and held it in her talons for a while, looking around, before jumping down to her shelf and bending her head to start feeding. If she happened to let it slip and it fell to the floor of the cage, she dropped like a stone and stood guard over it, mantling her wings above it protectively and glaring fiercely around before seizing it again and carrying it back to the perch.
Mumble didn’t object to my watching her eating, being wholly absorbed in the business of holding the chick down with one foot while dipping her head repeatedly to tear chunks off it. After each bite she would raise her head again with her face upturned, to straighten her throat and ease the swallowing process. She seemed to close her eyes as she bent down, and half opened them to slits as she reared up to swallow her mouthful down with a couple of big gulps. She often left the legs until last, and the occasional sight of her eating them from the thick end was mildly disturbing – she ended up with a little, vaguely humanoid ‘hand’, or even a pair of them, sticking out of the corners of her bill until they disappeared with a final couple of gulps. When she had finished eating she usually ‘feeked’ – stropped both sides of her beak against a perch, presumably to clean it of drying blood and yolk. (She also often used to bite and rub at her perches between meals, presumably out of an instinct to keep her beak honed down; if the upper mandible grows into too long a hook it may impale the food awkwardly. The pinewood edge of Mumble’s big tray-perch was a favourite whetting-stone.)
Mumble’s interest in her food even seemed to extend to the logistic side of things. On one occasion she was free in the kitchen while I was reloading the freezer cabinet with day-old chicks from a sack. She paid very close attention, sitting at first on my shoulder, and watching with what seemed to be rapt interest as I counted them into plastic bags. When I opened the freezer door she jumped to the top edge of it, head between her feet, watching the passage of each bag as I stacked them inside (I had a mental picture of her holding a clipboard and pen, ticking the bags off on a loading manifest). When I finished stacking the cabinet with a rock face of plastic-wrapped chicks, she even tried to get inside with them, clinging on to the icy ledge at the bottom and flapping her wings for balance.
You may hear it said that birds of prey do not drink, getting all the moisture they need from their food, but nobody who holds that opinion has ever shared quarters with an owl. When Mumble was out in her balcony cage I would quite often catch sight of her sitting on the edge of her water dish and dipping her head down between her toes. She would delicately scoop up sips of water and then tip her head back to let them slip down, visibly swallowing, with her throat working and eyes blinking. One evening in her second year I walked into the kitchen to discover her sitting on the edge of the washing-up bowl in the sink and moving her head around under a dripping tap, letting the drops fall gently into her open beak. After this I would sometimes deliberately leave the tap dripping for her, with a sponge placed below it to stop the noise driving me crazy.
* * *
No honest account of life with an owl can ignore what we might delicately call ‘the disgusting bits’.
Unlike daytime raptors, owls have no crop or ‘storage cupboard’ in their throat, but a two-stage stomach. Since birds have no teeth and cannot chew their food they swallow it whole, and this means that fledglings have to learn to tear their prey into swallowable chunks. While Mumble managed her habitual chicken dinners efficiently, in later years after we moved
to the countryside she was sometimes over-ambitious with the unfamiliar prey that she occasionally caught for herself ‘on the hoof’. The sign that she might be regretting her greed was an apparently uncomfortable immobility, sitting ramrod-straight on her perch with eyes slitted and upturned face stretched tight, and somebody’s tail protruding from her half-open beak.
Once successfully swallowed, the food passes into the ‘pre-stomach’, where strong acids and enzymes break it down. As already mentioned, to power its demanding lifestyle an owl needs roughly 20 per cent of its body weight in food every day, so the digestion process has to be relatively fast and simple to clear the way for the next meal. The hard or indissoluble parts – bones, teeth, beaks, insect wing-cases, fur and feathers – then pass down into a gizzard or ‘lower stomach’, where, to save time, they are formed into pellets for regurgitation. (It is sometimes assumed that only raptors produce pellets, but in fact hundreds of species of birds do this – in Britain, for instance, these include not only kingfishers and herons, but also rooks, starlings, tree sparrows and even robins.) Meanwhile, the useful bits are absorbed for nutrition, and – inevitably – that produces waste that has to be excreted.
Since birds do not have a separate bladder for urine (one of the many weight-saving modifications to their innards), an owl’s ‘unified’ droppings are a strongly acidic, foul-smelling brown-and-white sludge. This is expelled backwards horizontally, with some force – a procedure known to falconers as ‘slicing’, which resembles a tobacco-chewer spitting out a thick stream of evil brown juice. Anyone carrying a bird on their fist quickly learns to keep half an eye at all times on the direction in which its tail is pointing – and particularly when innocent civilians step up close to admire it. Since you only get between two and three seconds’ warning, it’s important to be alert for the signs of imminent action: a slight crouch, a thoughtful expression, followed immediately by tails-up, a parting of the fluff, and – ‘Torpedo los!’
The Owl Who Liked Sitting on Caesar Page 15