The rise and fall of the starling

ANOTHER LIFE: A couple of fistfuls of spruce seedlings, set close in the middle of the acre in its windier days, today make a tall, dark grove with just enough light inside to cosset a pair of apple trees. Magpies come to the conifers, teetering on their topmost buds like cockerels on weather-vanes.

Winter fieldfares pause there, too, in their restless quarterings of the hillside. And, coming up to dusk the other evening, the trees were suddenly taken over by a fall of a couple of hundred starlings, their ceaseless twittering drowning out all other sounds.

The spruce grove is not big enough for a main roost, and, perhaps, we should be grateful for that. It is, however, ideal for the "pre-roost assembly" which is part of the starlings' strategy for getting safely to bed in the bigger, denser belt of conifers that shelters the farmhouse down the hill.

The flock's general idea is to avoid the neighbourhood predators - peregrines, kestrels, short-eared owls - by gathering in smaller numbers in fields or bushes, and then either making a dash for the main roost in solid little parties or joining up in a mass aerobatic display that leaves their enemies confused.

In north Dublin, I'm told, little flocks of starlings gather thickly on the tall television aerials around Mountjoy Prison and then, as if on a signal, swirl up and fly in a circular cloud before descending into the prison's old chimney stacks, like genies restored to their bottles. Here at Thallabawn we treasure memories of similar manoeuvres, silhouetted dramatically against a winter ocean sunset.

It was not so much the size of the final flock that impressed us (a couple of thousand birds, at most), but the eerie intentness of their togetherness. The shape of the cloud of birds in the sky was as sharply defined as an airship or a flying saucer. Yet the birds within it flowed and pulsed in seemingly random waves. A sudden convulsion would twist the cloud into an hour-glass, or clench it to a tight, black fist. It would writhe and split and rejoin, but the egg shape would reassert itself like the physical form of a corporate avian intelligence.

Starlings in a flock are keeping station with companions in three dimensions, all changing direction unpredictably in a fraction of a second.

It helps to have the starling's incredibly mobile eyes: they can be swung forwards, upwards and backwards, and focused on both near and far objects in the same field of vision - but who, as it were, decides what happens next? For a long time it was thought that birds in flocks were flying on a follow-my-leader principle, like squadrons of fighter planes. Then frame-by-frame analysis of filmed flight sequences suggested something more like the corner-of-the-eye awareness mastered by the chorus-line of Riverdance. The ultimate solution to the starlings' spectacular precision and co-ordination will undoubtedly be something simple and instinctive, but it still has to explain how such apparent discipline is conjured out of chaos and chance.

It is now the best part of a decade since the starlings roosted on our hillside in winter in such an impressive flock. Those we see now are no more than the sum of juvenile birds, born last spring on the farms around and joining up in little flocks from June onwards. What seems to be missing is the traditional winter boost to their numbers from huge flocks of starlings migrating from continental Europe. Remarkable declines in starling numbers have been reported from much of north-west Europe and also in Britain, due perhaps to the loss of insect food for chicks on intensively farmed land.

IN his recent book, The State of the Nation's Birds, Chris Mead asked with concern: "Is the starling going to disappear just as quickly as it arrived two centuries ago?" The European starling, Sturnus vulgaris, has been one of the most successful birds of its kind (explosively so in North America, after 60 English starlings were released in Central Park in 1890). But its westward spread as a breeding bird reached these islands late, extending from bridgeheads in the north and west of Scotland. And while the starling nested in every Irish county by the start of the 20th Century, it hadn't fully colonized the far south-east until about 50 years ago.

On such a pastoral island, its impact has been largely welcome. The starling's huge appetite for grassland "pest" insects, such as leatherjackets, has been beneficial, here as in New Zealand, where sheep farmers encourage it to breed by fixing a nest-box to almost every fence post. Russia, too, has installed nest-boxes by the million.

The disappearance of permanent pasture may be one cause of European decline, together with intensive use of toxic agrochemicals. Climate change may have diminished the flow of winter migration to Ireland, though some of Leinster's flocks are still impressive.

The first urban roost ever recorded was in Dublin's downtown plane trees in the 1840s, when the starling was the "stare" (an Old English word for the bird) and bought for food in city markets. Some 200,000 starlings were roosting in the Phoenix Park at that time, and by the 1950s their winter numbers there were considered "beyond possible estimation".

Roosting in large numbers, starlings give off heat that can be felt 10 metres away, and a smell that reaches even further; their weight and insanitary habits can actually damage plantation trees. That can be one downside, so to speak, of the species.

One of the roost's main functions is to serve as an information centre, leading the birds to new sources of food, as the mass of starlings disperses in small flocks at morning. With a different pattern of farming - fruit orchards and vineyards, say - there would certainly be new problems. Even now, a farmer may find a field of late-sown winter barley tugged up, or his cattle-yard blackened with birds filching grain from the cows.

Without agriculture, Sturnus vulgaris would never have bred to its peak numbers, probably reached in the mid-20th century. Now the pendulum seems to be swinging back, to some fresh - but still "unnatural" - balance with humankind.Eye on NatureOn Saturday, January 26th, I was birdwatching at Sandycove, Co Dublin, where I spotted a grey seal munching on a seagull. About 15 blackheaded gulls tried to mob him and kept up their dive-bombing for about 15 minutes. The seal was either just snapping at them out of annoyance, or else trying to catch another.

Jacinta Egan, Monkstown, Co Dublin

Early in January, in J. F. Kennedy Park, near New Ross, Co Wexford, I observed that the muddy bottom of a pond was stirred up, apparently by some disturbance at the bottom. Frequently gas bubbles issued from the bottom of the pond. Could this have been frogs mating, or is it a little too early?

Joe Flynn, Enniscorthy, Co Wexford

It could have been the male frogs stirring at the bottom of the pond (where they hibernate) as they awaited the arrival of female frogs. All over the country they are stirring earlier this year, perhaps in response to global warming.

Several families of ravens nest on the cliffs on the other side of our valley. I normally see them in pairs or with their brood, but sometimes family groups unite, maybe a dozen or more, when the peregrine invades their territory. Once I watched about 50 birds riding the thermals from the cliffs and putting on a most marvellous acrobatic display. Is it normal for ravens to come together in such large flocks?

David Keegan, Coomhola, Bantry, Co Cork

Obviously they came together to enjoy the thermals, but they would also gather around a source of food like carrion.

Eye on Nature is edited by Michael Viney, who welcomes observations sent to him at Thallabawn, Carrowniskey PO, Westport, Co Mayo. E-mail: viney@anu.ie. Observations sent by e-mail should be accompanied bya postal address.