NOBODY blessed with a moderately analytical mind could dismiss my mega-simple theory - one that I have embraced for the past few weeks - that if you remove the food supply of a pest it will flit to pastures new. Until my neighbour, a farmer, sold several fields, the sky was regularly blotted out by swirling masses of discordant, defecating seagulls, enticed and fattened by his fertilisation programme; namely, spreading daily surpluses of shellfish from a nearby factory on to his acres. Since the last trailer-load was dumped I have not seen a solitary seagull. Maybe the birds now get their molluscs from the sea, where they belong.

Dumfries, some 17 miles distant from the erstwhile fast-food fly-in, has been plagued by gulls for years. Dead gulls block drains; they may carry salmonella and E-coli alive or dead. Alive they ''dive-bomb'' the populace; they ransack bins and deposit so much faeces that the locals are glad that cows cannot fly.

Now the burghers are advocating draconian methods of ridding the town of what they call ''rats on wings'', including lacing their feed with narcotics and taking up a Wishaw company's offer to provide a hawk and a falcon three days a week for three months.

The firm has achieved a measure of success on anti-pest projects administered by United Distillers and the Scottish Exhibition and Conference Centre, and it could be in ever greater demand by all manner of businesses, not least car companies forced to spend up to #10,000 a year to wash gull ordure from their forecourt motors.

Dumfries councillors are alarmed that gulls no longer nest in the lower reaches of the River Nith as readily as on the flat roofs of large buildings such as hospitals, office blocks, schools, and department stores. A sub-committee is set to debate various control measures.

Seagulls, which exist on a mixed diet, containing a smorgasbord of chips, kebabs, and titbits proffered by visitors and natives, are endemic along the riverside at the Whitesands.

Councillors want a cull. Every single method of controlling the airborne vermin seems to have its drawbacks, though. For example, officials have warned that lacing bait with a sleeping drug is a ''difficult and sensitive operation which can only be carried out by specially trained individuals''.

Iain Holt, of the wildlife and habitats branch of the Scottish Office's Agriculture, Environment, and Fisheries Department (SOAEFD), has pointed out that shooting is taboo in an urban area and noted of narcotic baiting: ''There is always a risk of accidentally disturbing the birds, resulting in large numbers of half-narcotised birds crashing down over the town centre. This again could cause enormous public concern.''

Gulls may be excluded from possible nesting sites by special netting fitted at a steep angle and prongs and spikes affixed to roofs and chimney stacks. Tensioned wires may be placed above roof ridges to interfere with flight patterns, although these methods call for regular maintenance.

Systematic removal may be considered and, more probably, egg oiling and pricking, although each calls for a labour-intensive programme over a number of years. Scaring, moreover, is ruled out in an urban environment.

Better by far to rob the gulls of their food supply, to re-educate the public about feeding birds (by hand or by trailer), and to re-design litter bins to make them gull-hostile. Council tips, too, may have netting installed to deter birds.

''Given the extent of the problem and the sheer number of gulls which have managed to breed unchecked, your councils are obviously now faced with a control strategy of huge proportions, for which there are no easy or quick solutions,'' Iain Holt wrote to Councillor Tom Holmes, of Dumfries.

According to the Royal Society for the Protection of Birds, gulls have been associated with Dumfries for hundreds, if not thousands, of years, and have always had a good food supply, although it is only in recent years that they have begun to nest in the town. The society says seagulls are preferable to rats and other scavengers that would replace them if they were no longer there.

There can be fewer folk more pessimistic than Dr Keith Hamer, a lecturer in animal ecology at Durham University who, after 14 years of studying sea-birds, believes seagulls are here to stay.

The Hamer paradox is that the more you move seagulls on from what is, from the birds' point of view, a very good site, the more gulls come from other less desirable colonies.

Says Dr Hamer: ''Large gull populations may be moved on, as happened on the Isle of May, but others simply move to the vacant nesting sites.

''Young gulls are looking for somewhere to breed, and there are always more of them than there are breeding sites.

''Culling or egg-piercing always has to be very long-term and may cost many thousands of pounds. Gulls are very, very adaptable, and we have created the habitats for them, buildings which are similar to, but safer than, the traditional cliff-top.

''Dumfries has ample food supplies, including a big tip not very far away. If poison is used to cull them, it does not act immediately, and the end result is gulls falling out of the sky.

''Every town in the country that has tried to cull has given up in the end. They can breed for 20 years and are long-living birds. There is no evidence that birds of prey work.

''Putting prongs and things on building sites also tends to move gulls on to other buildings. Gulls are pretty well here to stay. Yes, I am pretty pessimistic.''