The Owl Who Liked Sitting on Caesar (13 page)

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In the wild, the mortality rate among any one year’s tawny owlets varies considerably. Regional differences, and the sheer difficulty of carrying out statistically significant studies in thick woodland, mean that few confident general conclusions have been published. However, one thing that does seem quite clear is that an owlet’s early survival chances depend upon the local supply of prey animals, and that this varies widely over cycles of a few years.

By some mechanism that science has not yet explained, owls are among the species that seem able to adjust their brood sizes in advance to match the cycles of prey numbers in their area. In a very ‘bad vole year’, Tawny Owls in that area will not lay eggs at all; in a marginal year
clutches will be small, and one or more of the hatchlings will certainly fall victim to competition in the nest; but in good prey years the clutches are larger, and fewer fledglings die before they become independent. A good food supply also means a shorter fledging period, and studies show that owls that fledge earlier tend to live longer – presumably because they are stronger and more self-reliant when the leaves drop and the weather begins to turn cold.

Although Tawny Owls are noted for being splendidly fierce defenders of their nests and young, and will not hesitate to attack even humans when they perceive a threat (more than one naturalist has lost an eye to a tawny attack), the owlets are naturally vulnerable to predators as soon as they start to explore their surroundings. While they are always in some danger during their clumsy early expeditions, the degree of risk from predators – in Britain, mainly from jackdaws, sparrowhawks, goshawks, buzzards and foxes – seems, again, to be correlated with the local supply of small prey animals. To some extent the predators’ diet overlaps with that of the owls; if rodents are plentiful the predators are less of a threat, but if they are scarce then predators are more likely to catch owl fledglings.

A Danish ornithologist calculated that in a bad year for voles 36 per cent of the owlets in his study area – and particularly those that hatched late – died before ever achieving independence from the parents; the overwhelming majority of these fell victim to predators, particularly foxes. A study in a northern English conifer
forest in a year of extreme prey scarcity calculated the Tawny Owl fledgling mortality rate at a staggering 91.7 per cent. However, the Oxfordshire study already mentioned concluded that in a plentiful prey year the mortality rate up to late July may have been only 4 per cent, and was certainly no higher than 16 per cent.

The death rate after the fledglings leave their parents and start trying to establish their individual territories is probably far higher, and perhaps as high as 60 per cent during their first six months of independence. The crucial early weeks will often demand fighting – or at least, convincing threat displays – against rivals (and Tawny Owls seem usually to be fighters rather than bluffers). The loud hooting heard on autumn nights is the sound of parents driving their broods away, and of neighbouring adult tawnies warning these adolescents off their territory. Simultaneously, the juvenile tawnies must learn to feed themselves by trial and error.

If they are lucky or fearless, they will find or win a territory fairly close by – either because a previous adult proprietor has died and left it vacant, or because the local density of adolescents is low and the competitors are less determined. It is noticeable that when tawny ‘landowners’ die (and there is some evidence that when one of a pair dies its mate may not outlive it for long), their vacant territory is not automatically taken over by the next-door neighbours. Tawnies depend for successful hunting not so much on the sheer acreage of their hunting range as on their intimate familiarity with it, so a property lying vacant
is more attractive to a juvenile seeking its first territory than to an established pair.

An owl needs to eat about 20 per cent of its own body weight daily. (Think about that when you next step on the bathroom scales; for me, it would mean digesting 34lb every day – the weight of seven volumes of the
Encyclopedia Britannica
.) If juvenile tawnies fail to catch enough prey to keep up their strength for the nightly hunts and confrontations of autumn and early winter, then they will soon starve to death. Even if they learn hunting skills quickly, heavy local competition may force them to search further afield for a permanent territory. (Occasionally, much further afield; the record may be held by a British tawny owlet that was ringed one May in Northumberland, and was recovered that November all of seventy miles away in Dumfriesshire.)

Even for young owls that do acquire a territory, and make a start on building up the necessary data bank of local information tree by tree and yard by yard, the first winter brings steadily increasing dangers both from hungry predators and from simple starvation. There is little reliable data for populations of British tawnies, but some statistics from continental Europe make pretty grim reading. In one Swedish study, the death toll among young tawnies was 67 per cent in the first year, and 43 per cent of the survivors in the second year – so of an original one hundred fledglings, only nineteen were still alive in their third year. Obviously, the first winter must present young owls with the harshest challenges, but it clearly takes more
than one year before they have established mastery over a consistently productive territory. (We might guess that the relatively high death rates in the second year may perhaps have something to do with failure to mate, and thus to establish a sufficiently large joint territory early in that year.)

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Despite their unjustly sinister image in folklore, there seems to be only one British example of owls being systematically persecuted by humans in the belief that they were competitors for a resource – but that episode was long-lasting, and distressingly recent. From the mid-nineteenth to the mid-twentieth century, all British raptors, daytime and night-time, were routinely massacred as ‘vermin’ by the gamekeepers of shooting estates, in the belief that this was necessary to protect the chicks (‘poults’) of the game birds that they were rearing in huge numbers for the guns.

The scale of this immense (and, as it turned out, senseless) slaughter began to diminish gradually after all birds of prey were given legal protection in 1954 by the first Protection of Birds Act, which was updated in 1967. Since the 1970s the belief that Tawny Owls took significant numbers of poults has been proved to be false by irrefutable large-scale studies undertaken jointly by bird-conservation and sporting bodies. Even allowing generous margins for error, these studies found that all birds of prey were responsible for only some 5 per cent of the poults lost to all causes, both violent and accidental, compared with at least
50 per cent taken by ground predators such as foxes, dogs, cats and mink. Imaginative co-operation between conservation and sporting interests has since reduced this proportion even further.

Sadly, however, the myth has been so persistent that even today some Tawny Owls still fall victim to illegal, indiscriminate and barbarically cruel pole-traps. Luckily, since tawnies seem virtually never to eat carrion, they are not vulnerable to the poisoned bait that some keepers still spread around, killing significant numbers of other raptors – especially in Scotland. (Again, even if a build-up of agricultural chemicals in the systems of prey animals is indeed a factor in owl mortality, then tawnies are less vulnerable than Barn Owls, because they take their prey mostly from woods and parkland rather than from the cultivated farmland where most chemicals are used.)

In most of lowland Britain the greatest threat mankind seems to pose these days is through owls colliding with overhead cables, wire fences and – particularly – motor vehicles. Like high-hovering kestrels by day, they find good hunting along road verges, but their low-level night flights put them in vastly greater danger. (One report noted that on a thirty-mile stretch of road in Dorset, seventy-six owls had been killed by traffic in six months – and those were just the corpses that were found actually on or beside the road.) Even so, British studies suggest that our Tawny Owl population has remained fairly stable over recent generations, with an annual mortality rate averaging about 20 per cent among mature birds. The healthy overall
numbers certainly show that enough of them breed and rear families successfully to sustain the national population.

Individually, however, a life in the wild is always high-risk; although one ringed tawny was recorded as reaching the truly astonishing age of twenty-one years and five months, their typical life expectancy seems to be only about five years. Depending upon your emotional responses to the natural world, you may or may not consider a wild tawny’s life to be nasty and brutish, but it is certainly short. I continue to take comfort from the thought that Mumble never had to take her chances in this merciless lottery.

AT THE BEGINNING
of 1979 Mumble was a fully grown, fully feathered owl, and in the months to come both of us would have to get used to some of the implications of that. In the wild, she would by now have acquired – and would be defending – a hunting territory. I supposed that in our first months together she had come to regard me, the provider of food, as her mother, but might she now begin to see me as a rival intruding on her turf? I would have to keep a close eye on her attitude and behaviour not only towards me, but also towards other people.

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Mumble is still reasonably friendly with visitors, and I don’t yet see any evidence of strongly expressed territorial feelings. I never have her loose about the flat when I am expecting anybody, of course – the ring on the doorbell might turn out to be the caretaker, and anyway it would
be stupid to risk her exploding out the door past some startled visitor, to go zooming around the public passages and crashing into fire-doors.

If I am urged to bring her in from the balcony cage by somebody who has already arrived and has settled in, I always warn them that it might get a bit exciting. Male friends tend to wave aside my caution, out of genuine curiosity mixed with a hint of machismo – and indeed, when I bring her in and let her loose she doesn’t seem actively hostile. She may fly to her door-top perch while she checks them out, but quite often she goes off about her own business, leaving the humans to it. However, both I and any visitor may well get the ‘shooting gallery’ treatment if we move about the flat.

She will be sitting quietly in the shadows on the telephone table at the far end of the hallway, apparently not paying any attention to us – but when anybody walks across the near end of the hallway between the living-room and kitchen doors they are liable to find her swooping out of the twilight at high speed, aiming for their feet. Considering the brief window of opportunity provided by the couple of steps across the 4-foot-wide passage, her reactions are incredibly fast (I imagine that in the night-time woods a lot of mice and voles must die without ever knowing what hit them). Whether or not the attraction of human feet is always the amusing shoelaces, I can’t be sure. If – as usually happens – the walker freezes, for fear of stepping on her, Mumble skid-turns at the last microsecond and lands behind their feet, as if disappointed that
they have spoiled the game. Then she flaps briskly back to the ‘firing line’, to await their reappearance from the kitchen so that she can have another shot. [My friend] Will finds this highly amusing, and takes it as a challenge to his agility; other visitors might look a bit hunted, and make excuses to stay in the kitchen until I have stepped out first to draw the fire.

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If Mumble decided after a while to explore visitors more thoroughly, she could get so close-up and personal that they might have to display a certain amount of fortitude. Deceived by the picture-book image, they usually seemed to expect that an owl would provide more of a passive spectacle than she was prepared to be, and she sometimes treated them with the same rough familiarity that she showed me. She might try to eat their shoelaces, or – more alarmingly – she might play her ‘hunting for mice’ game down beside them on the sofa, with kicking feet and flapping wings. During her first few months in residence, about the most personal she would get with anybody else was occasionally to land on their shoulder and nibble gently at their ears and hair, but now she sometimes landed directly on their heads. Given my trade, I had several old military helmets around the place, and I began to issue these tin hats to visitors if Mumble was on the prowl. They might prevent an accident, and anyway they served as a useful reminder that an owl was a lot more than a cuddly toy.

I can’t recall exactly how old Mumble was on the
weekend afternoon when my neighbour and old mate Gerry had come in for a drink, and Will also turned up, bringing an American friend of his named Howard. Howard seemed quite relaxed about my eccentric domestic arrangements, and I knew that while he looked like the proverbial mild-mannered bookstore clerk he was in fact a captain of US Airborne Infantry, highly decorated in Vietnam. Still, he did have a very bald head, and since I didn’t have the authority to write him up for yet another Purple Heart I thought it sensible to dish out steel helmets all round.