Beak spots are a gull's best friend

THE little sand-spit at the end of the channel has a light all its own on a frosty sunny morning: an exactitude edging every grain of sand, a smooth polish to shapes and colours like the luminosity of tempera.

A line of oystercatchers pose, plump and glossy as Andalusian matrons, long beaks made even more vermilion by the blue sea behind them. Two or three balance on one leg (one leg each, that is) which no longer fools me, not even when they hop along monopedally before lowering the foot they have been warming against their bellies.

I used to feed a genuinely one-legged herring gull from the window of my bachelor pad in Ballsbridge and often wondered what accident it met with. Seals and otters, even cod and angler fish will grab at floating seabirds from beneath, but it was hard to imagine my penthouse visitor venturing much beyond Ringsend. Perhaps one-legged seagulls make their way to cities, like beggars after a war.

There are half a dozen herring gulls, too, on the sand-spit, and they also have a touch of red - just one brilliant spot near the tip of their yellow bills. I can never take note of this without thinking of Niko Tinbergen, whose classic experiments on gull behaviour upset me somewhat in my youth.

Newly-hatched herring gull chicks are programmed to peck vigorously at the red spot, whereupon the mother regurgitates a meal for them. What Tinbergen established. through presenting various model gulls heads to the nestlings, was that the chick responds to an abstract detail, quite divorced from the overall presence of its mother. A red spot at the end of something long, thin and yellow is all it needs.

Indeed, the chick would peck even more vigorously at a stick that was longer than the mother's beak and marked with a colour patch of even greater contrast - "a supernormal stimulus", as Tinbergen called it. This is the sort of trick, apparently, that cuckoos use, persuading gullible pipits to feed the one chick in the nest that gapes wide and squawks louder than the rest.

I can't remember exactly why any of this should have worried me: something to do with discovering how manipulative life can be.

Standing between the herring gulls and oystercatchers, as if wrapped in thought, is a group of petite, even dumpy little gulls with no red spots - common gulls - and on the other side a burly trio of great black-backed. gulls, equally pensive. It is useful, sometimes, to look at seagulls on a sand-spit, waiting together like strangers in a bus-queue. and be reminded of their different physique and demeanour.

Living at the Atlantic coast, one tends to take all the gulls for granted, as if the mere presence of the ocean underwrites their well-being. But the past 20 years have seen some remarkable declines in breeding populations of gulls. not all of them easy to explain. Those in the western counties, from Galway to Donegal, have been documented by a steady team led by the late Dr Tony Whilde of the Corrib Conservation Centre.

Between 1977 and 1993, the number of gulls breeding inland, on lake islands, declined by more than a third. Black-headed gulls were down by some 5,000, lesser black-backed by 1,800, common gulls by 1,200, herring gulls by 700. Even the great black-backed gulls nesting on Lough Corrib fell from 35 to half a dozen.

The biggest obvious cause has been botulism, a form of bacterial poisoning that gulls pick up at rubbish dumps. Clostridiun botulinum thrives in the humid, airless conditions of the black plastic bags in which we dispose of our waste, and in the grotty puddles that develop around the dumps.

Herring gulls seem especially vulnerable. They were tempted inland in Connacht initially, in the early of the century, by the waste dumped by bacon factories. Now, the species has virtually disappeared from the larger lakes of the west.

Does it matter? They are noisy, quarrelsome and aggressive, and get sucked into airplane engines. Ronald Lockley, watching herring gulls nesting on Skokholm, off Milford Haven, saw another side. In fact, these cold-looking, rapacious birds give the appearance of great tenderness and affection in their nesting affairs. You will see the male respond to his mate's begging attitudes by nibbling and caressing her bill and even appearing to feed her. The male also brings leaves, flowers and limpet-shells to the nest

It is not the gulls' fault that we have created such toxic squalor for their scavenging. And as Tony Whilde wrote in his Natural History of Connemara: "A decline of such proportions in any other species would have caused an outcry amongst conservationists and the general public."

Common gulls, by comparison, are quite demure, their spring flocks in the fields "resembling at a distance the snowy tents of some fairy potentate" as one of my books insists. The cause of their steady decline on the western lakes is hard to explain. Predation by mink is one suggest ion but mink do not occur so far near the main Mayo and Galway colonies.

These gulls rely substantially on earthworms and several dry springs may have caused a food shortage. Yet again, they are at the southern limit of their range when they nest in the west of Ireland. Their decline in Connacht coincides with expansion in north-east Scotland: perhaps they are moving north as European summers warm up.

Further to my comments or county council strategies for persuading drystone walls to stay put, a co-operative company called Cornerstone Ltd (at 3 Ardbrugh Close, Dalkey, Co Dublin) runs workshops all over Ireland on the building and repair of stone walls "in a traditional way, reflecting the style and methodology of each individual area

A new directory of "environmental-type groups", national and local, has been compiled by Ciaran Ryan of 9 Glenview Drive, Killarney, Co Kerry. It is arranged county by county and costs £4 plus P&P.