Nightingales in November (51 page)

Any young Tawny Owls that left their parents' territory earlier in the summer will also be in a similar position to those immature Peregrine Falcons, in that finding a place to feed and safely roost while not alerting any established territory-holding pairs as to their presence will be of the highest priority. With the odds seemingly stacked against
the young Tawnies surviving at this stage they have a couple of factors working in their favour. First, autumn is considered to be the peak period of abundance for many of the Tawny Owls' main prey items – mice and voles. The Wood Mouse, for example, is capable of producing litters of four to seven young in successive pregnancies from March to October, leading mammal expert Stephen Harris to estimate that a pre-breeding population of around 38,000,000 could easily rise to about 114,000,000 by autumn. This super-abundance of prey should therefore make it straightforward for even the most inexperienced of young Tawny Owls to catch enough to sustain life while honing their technique. Second, as the adults are still actively moulting in early September, they will not feel the need to put as much energy into fiercely guarding their territories as they would later in the year, meaning any young trespassing Tawnies could temporarily be given more latitude than might normally be expected from such a territorial bird.

Crucial to any Kingfisher's survival through to the following breeding season will be the maintenance of a territory in which the sitting tenant has exclusive fishing rights. Now should be the time when many of these territories are actively being secured, with many males taking possession of exactly the same stretch of river they will have held with their mate during the summer. Unceremoniously booted out, the frequently socially subordinate females have little choice other than to hold a piece of river-front that abuts their old territory, or if this is not possible, a stretch of waterside property reasonably close by. In the world of Kingfisher politics, however, adult females should still be above juveniles in the pecking order, with any youngsters making it through to September
forced to take whatever half-decent habitat they can hold without being chased away.

The famous ornithologist and Robin expert David Lack, in his wonderful monograph
The Life of the Robin
wrote: ‘From September onwards till May, the woodlands, parks, gardens and hedgerows of England are parcelled out into a great series of small-holdings, each owned by an individual or by a pair of robins.' Finishing their moult before the adults, those Robins that hatched earlier in the year will by now be sporting their first red breast and so should already have been practising the fine art of territory acquisition for a few weeks. However, by early September they will suddenly find the competition increases once more as freshly moulted adults also enter the fray. Recently voted the nation's favourite bird, maybe not as many people would have voted for the Robin if they had been made more aware of this bird's huge propensity for violence!

When not feeding or sleeping, Lack believed a large proportion of a Robin's life is taken up with either singing or fighting. After an uncertain couple of weeks while becoming accustomed to the plumage which puts them at least visually on a level playing field with the adults, the juveniles will have suddenly begun limiting both their singing and aggression to one particular area from which all other Robins will be excluded. To combat the adults' experience, the juveniles will often resort to violence much more readily, and although physical, any ensuing fight will rarely result in the Robins being seriously hurt. This fighting is not just confined to the males either, with some of the females keen to acquire a territory being equally pugnacious in keeping all other Robins at bay. Less inclined to fight than those youngsters busily proving themselves, the adult Robins more commonly rely on singing and posturing, with their red breast prominent, as the main
means of securing and holding a territory. As individual battles become settled, the countryside will slowly but surely be carved up into a whole series of interlocking Robin dominions.

Confining their territorial behaviour to just the period around when their chicks were reared means there should be little need for any aggression amongst the hordes of Blue Tits roaming local woodlands and gardens in their mixed feeding flocks at this time of year. Having started their moult as early as June, the adult Blue Tits in the southern half of Britain should by now be completing their moult, which will see the males looking particularly dapper in their electric blue caps. Retaining the vast majority of their flight feathers, the juvenile Blue Tits will still not begin to resemble their parents until their body moult is completed later in the autumn.

Mid-September

As autumn unfolds Robin activity will move centre stage, as the experienced adults enter the fray to compete with those birds barely four months old for that all-important territory which could mean the difference between life and death. For beauty and complexity the Robin's song is often considered to play second fiddle to that of the Nightingale's, but while the latter's song is confined to just south-east England and only heard for a brief period between mid-April and the first days of June, the Robin not only geographically serenades most of Britain, but is also heard for most of the calendar year too. When attempting to describe the Robin's song it has been invariably described as ‘a distinctive, cheerful and varied warble', but scientists studying the song are discovering its structure has a surprising level of complexity.

When singing, the Robin utters its song in a series of short bursts, with each burst lasting little more than two or three seconds before being interspersed with a short pause. A bout of singing can often last a few minutes and may often consist of dozens of different bursts of song, each of which can be further broken down into around four to six phrases that last, on average, around half a second each. The French ornithologist Jean-Claude Brémond, who has specialised in bio-acoustics, documented the Robins he was studying as having a repertoire of more than 1,300 different phrases, which when placed together in a constantly varying sequence were theoretically able to create an astronomical number of permutations. By experimentally manipulating pre-recorded Robin song, Brémond also discovered that the different phrases tended to alternate between high and low pitch, and despite the birds being potentially able to produce endlessly variable songs, it is highly likely that all the local Robins become familiar with the basic characteristics of the songs of all the birds in their immediate neighbourhood. Recognising a neighbour's voice will mean that a territory-holding Robin need not waste any time and energy on an aggressive response, saving it instead for when a ‘new' voice is heard. Any unfamiliar song suddenly heard in a familiar place, which may represent a newcomer threatening to upset the status quo, will then instantly trigger a call to arms for those territory owners within earshot.

In addition to the song's complexity, volume also plays a key part in helping to convey meaning for the Robins at this crucial time of year. Encroaching birds intent on securing a territory will often begin with a cautiously uttered song from low down in the bushes. Only when no opposition is encountered will the newcomer then gradually ratchet up the volume to a level where the song can be belted out from the tree-tops as it attempts to claim the territory for itself. In those territories already occupied, possession frequently
seems to be ‘nine-tenths of the law', meaning the owner is usually able to drive the interloper from the premises. So clearly marked are these Robin territories that if a bird suddenly disappears, the surrounding neighbours will quickly extend their boundaries to fill the vacant lot, so that the ground will often be fully occupied again within just 24 hours. At this stage the plaintive and wistful ‘winter song' is the warble of choice and will be heard right the way through until they change their tune back to the full-blooded spring song around Christmas. Regardless of the seemingly more laid-back tone to the winter song, it is still primarily concerned with conveying one simple message: ‘back off… this is my territory'.

Now unshackled from the needs of their youngsters, the adult Tawny Owls will be quietly left to their own devices at this time of year. Sporting fresh flight feathers, the adult Tawnies will need until at least early December before their entire annual moult is finally completed. Remaining on territory for the duration, and needing only to find sufficient food for themselves, it will still be a few weeks before the pair begins reasserting possession of their dominion. Most Tawny Owls are considered to be a model of monogamy from year to year, with a Finnish study revealing that 67% of females only bred with one male during their reproductive lifetimes. It is also likely that a high proportion of the remaining 33% were only forced to find other partners upon the disappearance of their original mate, making it very much a case of ‘till death us do part' for many Tawny Owl relationships.