A kind of home making

The grey crow was perched on a branch of the old spruce tree at the gate and tugging hard at a thin, whippy twig that had quite lost its needles in the winter. Crows always prefer to break off fresh twigs for a nest (they're stronger and more supple and stay in place better than brittle twigs collected from the ground), but anyone could have told the hoodie how stubborn a sinewy spur of conifer can be. At last, after losing its grip and floundering near to a fall, it gave up and flew off, empty-clawed.

The birds I shall really keep an eye on for any nesting plans are a little flock of half-a-dozen goldfinches who have turned up each morning for weeks at the peanut feeders in the hedge (or perhaps it's a different half-dozen each day - who's to know?).

With their black-and-scarlet masks and vivid yellow wing-bars they have an almost tropical brilliance among the bare twigs of fuchsia and hawthorn, quite outshining the greenfinches, chaffinches, tits and sparrows they fight with at the nut-baskets.

Goldfinches, like siskins (the finches of conifer forests) have only lately discovered the convenience-food of garden birdtables, and even a daily attendance says absolutely nothing about their later intentions. Our visitors fit the picture of an ordinary little winter flock - a "charm" of goldfinches, in the gracious old term - roaming around, like the greenfinches, and discovering this hospitable oasis with its apparently inexhaustible refills.

They will eventually have to nest somewhere, however: why not here on the acre? Orchards used to be the place, in days when the countryside had them. Now it's "areas of scattered trees and shrubs, in cluding parks and gardens, close to open land where food plants grow" which should leave our unruly acre, with its wild and weedy bits, right in there with a chance.

But are the trees tall enough yet? Goldfinches seem fussy about this. They usually build "high on a swaying bough, four to 10 metres above the ground", the nest a neat weave of mosses, spider-silk and lichens, "with a deep cup to retain the contents in windy weather". We can offer alders and sycamores, even an oak or two that are coming up to size. But the goldfinches, now clinging on to the nuts as they swing wildly about in a rising sea-wind, may file the experience away: there's swaying, and there's losing your eggs like pebbles from a slingshot.

March is, in any case, a tricky month in which to read the minds and behaviour of birds. Global warming may pull courtship dates one way but a cold snap can put everything on hold. Roaming flocks of finches and tits still speak of winter, yet in some of them the process of pairing is already under way. All birds time their eggs and young to coincide with optimum food supply. Blue tits and great tits that live in oakwoods, for example, time their first broods for the abundance of spring caterpillars feeding on the oak-leaves.

But the caterpillars, in turn, are timed to eat the oak-leaves just as they break from their buds and before the trees can pump too much tannin and other phenols into them as a defence against being chewed. Neither caterpillars nor blue tit chicks do well on the "poisoned" leaves. So it's really the trees that decide when blue tits should start courting - I like that.

Finches, too, have their priorities. The chaffinch feeds its chicks mainly on insects, so it lays early, like the tits. But the goldfinch feeds its young mainly on thistle-seeds (hence a beak shaped like a tweezers), so it doesn't bother nesting until early May. That makes a rather long time to be bribing them with peanuts.

Meanwhile the robins can be counted on to start building any time now, so this is the day to decide if you want to help Gavin Fennessy at UCC with his nest and habitat study. It means watching out for a female carrying nesting material and seeing where she goes, then keeping a discreet but regular eye on a nest and entering details on a card - when the eggs are laid, how many, when they hatch, when the young open their eyes and get feathers, and so on.

Since the study began two springs ago, Fennessy has been able to feed his computer with the details from more than 600 cards, mostly kept by people in rural areas. Ulster and Munster have shown particular enthusiasm, but far fewer cards have come from Leinster and fewer still from Connacht. The records at this stage are interesting, rather than startling, raw material, and comparisons with British studies will help sort out their significance.

Robins are much more common in Ireland than in the UK, which may say something about the relative importance of our hedgerows. Our birds lay, on average, rather smaller clutches of eggs, but more of the chicks survive to fledging age. Even so, more than a third of the clutches will not result in any fledged chicks. Cats are the commonest predators, and desertion of the nest is another big factor (how often in this sample, I wonder, because of over-enthusiastic inspection by the observer and assorted human broods?).

Contact Gavin Fennessy at the Zoology and Animal Ecology Dept, NUI Cork, Lee Maltings, Prospect Row, Cork