ANOTHER LIFE/Michael Viney: Once, kicking my heels in Boston on a raw, grey Sunday in March, I prevailed upon the young cultural attache at the Irish embassy to drive me out into the countryside to watch birds. Hunched beside leafless birches, he professed to share my delight in a sighting of the black-capped chickadee, a bird we might have found just as easily - even, perhaps, fed by hand - in a city park.
Half my pleasure in the chickadee, however, lay in the onomatopoeia of its name, along with the affection implicit in its tumbling syllables. By comparison, the naming of our own equivalent species, the blue tit, sounds positively dumbed down - not even the "titmouse" or "bluebonnet" of the past.
But jollier names did not always breed indulgence for Parus Caeruleus, let alone free food. In 18th century Hampshire, Gilbert White noted the bird's fondness for flesh, "for it frequently picks bones on dunghills: it is a vast admirer of suet, and haunts butchers' shops. When a boy, I have known 20 in a morning caught with snap mouse-traps, baited with tallow or suet." It's in the run-up to April egg-laying that the female blue tit, in particular, ranges most restlessly for food.
As her reproductive equipment swells and the yolks begin to line up in her egg duct, her weight shoots up from less than 11 grams (three dry tea-bags) to almost 14. Unlimited peanuts certainly help her energy; so, sometimes, does the nectar from shrubs such as the early flowering currant.
But the big spring effort in foraging is devoted to insects. The willow tree that leans across our stream is now a great dome of silver-green catkins, and tits have been rummaging there for aphids and tiny flies, using bill and claw in a close examination of the flowers; they may also have been eating the pollen, a rich source of protein. Let a blue tit into your livingroom around this time, and it may begin stripping the wallpaper, hoping for sweet sap or a spider beneath the "bark".
But while the tits are building up their own strength, their big decision about when to mate and lay eggs is tied into the peak supply of one particular kind of food for their nestlings. And that, in one of ecology's more challenging linkages, involves entirely unpredictable events. However much drawn to back gardens, blue tits are still woodland birds, reaching their highest density in oakwoods such as those at Killarney. Here it is the spring hatch and growth-rate of caterpillars that determines the amount of food available to the young tits, a whole brood of which - perhaps 10 or 11 nestlings - may eat up to 1,000 caterpillars in a day.
These are mainly the young of various moths that feed on the early leaves of the oaks. Indeed, they need to pounce (if the word is appropriate to caterpillars) before the leaves become dosed with tannins and phenols which are the oaks' defence against being eaten. Tannin-free caterpillars grow bigger and faster and are also more digestible to young tits.
Crucial is the date of the oak's bud-burst and the warmth of the spring (which also governs the caterpillars' development).
The start of the caterpillar supply and its duration are quite beyond the blue tits' control, yet they would theoretically need to get into a state to start breeding about four weeks before it happens. The variables in all this, not to mention the impact of global warming on the date of bud-burst and the tits' sense of timing, are now the stuff of some dedicated ornithology.
Scientists appreciate the blue tit because of its big and robust families and its readiness to raise them in handy nest-boxes with removable lids.
Indeed, Parus Caeruleus has been chosen as the model species for evolutionary research by behavioural ecologists from six countries who set up the European Blue Tit Network in Germany last autumn. Typical of their interests is the geographic variation and evolution of blue tit song. No one in Ireland, to my knowledge, seems all that curious about the Kerry accent of Killarney's blue tits (which may differ, perhaps, from the description in the Collins Bird Guide: "Song a couple of drawn-out, sharp notes followed by a silvery trill on lower pitch, siiih siiih, si-surrrr").
But I did enjoy the study, a few years ago, by a young woman scientist at the University of Ulster, which set out to measure the contribution of peanuts to the energy requirements of back-garden tits in the Belfast suburbs. Feeding and watching them daily over five years, she actually learned to tell one tit from another, identifying her resident birds and a few "regular intruders" from their plumage patterns.
HERE'S how you do it: "In blue tits, variations in the colour of the crown, size and shape of the white forehead patch, the width of the white supercilium (stripe over the eye) and nape band encircling the blue crown, the width of the dark eyestripe and nape band, and the width of the dark border around the white ear coverts, all combined to give an individual an identifiable head-pattern." Just now, of course, most female blue tits are busy laying or incubating, a job which will leave them with a "brood patch" on the belly - a bare patch of skin with an extra flow of blood at the surface to keep the eggs warm. They are laid one a day, and covered with a wad of nesting material when the female goes out to be fed by her mate or look for food herself.
At the last-but-one egg, usually, she settles down to incubate for about two weeks: when you see her fly out with a piece of eggshell and the male flies in with the first small caterpillars, the genes are on their way again.