It is a problem that has stretched the imaginations - and in some cases, budgets - of almost every local authority in the country.

The consensus among property owners and town centre managers is that pigeons are a costly nuisance, capable of destroying buildings and spreading disease.

Over the years, frustrated burghers have employed a variety of methods to rid the streets of pigeons and their attendant debris.

London's Trafalgar Square, where pigeons are tolerated because of their tourist pulling-power, costs an estimated �75,000 a year to clean up.

Pigeons can cause damage to buildings where they nest and roost

Elsewhere, shooting culls have been tried and tested, but are acknowledged to have limited effect - although is not uncommon for private companies to hire snipers to shoot birds off their buildings with air rifles.

Pest controllers who have a MAFF licence can orchestrate culls with poison pellets.

Narcotic-laced food, which has the effect of knocking birds out, is placed in appropriate locations. Doped birds are then examined so "non-target species" are released and pigeons necks are dislocated.

Pigeon pill

In other parts of the world, inventive attempts to keep a lid on pigeon populations have even included experiments with pigeon contraceptives.

Switzerland's trails of the pigeon pill, however, proved to be ineffective - fertile birds from other areas managed to infiltrate flocks, and it was difficult to limit the drug's effect to pigeons only.

And plastic models of birds of prey - which, judging from Websites, are pretty popular in the US - only seem to scare pigeons for a short time.

A plastic hawk, manufactured in the USA to scare pigeons

Companies like the Warrington-based Network Pest Control Systems work to develop and provide pigeon deterrents.

Sales marketing manager Iain Turner said: "Pigeons and the mess they create are certainly a problem for many private companies as well as local authorities.

"Droppings deface buildings and can in the long term destroy them.

"As well as that, there are health risks associated with pigeons - they can carry salmonella, and inhaling particles from droppings can lead to a disease called ornithosis, which is potentially lethal.

"Culling doesn't really work in the long term - the birds always come back - and it is extremely unpopular with the public."

Replica owls are also on sale in the US

The company manufactures systems including nets, which screen off potentially attractive nesting and roosting sites, as well as wire spikes and coils which are placed along ledges to discourage birds from landing.

One town which reckons it has the pigeon problem licked - and at minimal cost - is Hanley, in Stoke-on-Trent.

Town centre manager Malcolm Hawksworth launched an unusual offensive on his feathered foe.

He said: "Through our research we established what didn't work, namely, killing pigeons - they always come back.

"We also established that it was not worth prosecuting the occasional person who insists on feeding them.

'Amazing deterrent'

"Effectively, pigeons are airborne rats, but you always get one sad person who goes into town every day to feed the pigeons, and the best policy is to ignore them."

Mr Hawksworth wrote to businesses in the town centre, encouraging them to reduce the "pigeon friendliness" of buildings.

He also encouraged visits from a local birds of prey sanctuary, which is now a licenced stallholder in the town.

Devices can be placed on buildings to make them less pigeon-friendly

He said: "The deterrent effect of a harrier hawk or a Step eagle being in the centre is amazing. The eagle just has to stretch its wings and the pigeons take flight and do not stick around."

The town's policy of encouraging street entertainers also helps to control the pigeon population, says Mr Hawksworth. "They don't like the noise," he said.

But the town's major breakthrough has been in spreading the word that feeding pigeons is socially unacceptable.

The Tidy Britain Group - which is launching a campaign discouraging people from feeding feral birds - says this is the key to solving the problem.

Spokesman Peter Gibson said: "Research seems to suggest that the best way of dealing with it is to take away the pigeons' food source.

"We hope that people will think before they feed pigeons. It is not natural for pigeons to rely on human beings for their food, and we now have populations of lazy urban birds."

'No favours'

The TBG says a recent survey in Birmingham revealed that people fed birds a) because they thought it was a kind thing to do, b) because they did not want to waste left-overs, and c) because in some religions, like Hinduism, feeding animals is a spiritual necessity.

Mr Gibson added: "People have to realise that, however well-intentioned, they are not doing pigeons any favours by feeding them."

But not everyone agrees. Many animal-lovers passionately defend their interaction with pigeons.

'We admire the pigeon'

Andrew Tyler, of the Charity Animal Aid, said city dwellers in particular valued their contact with pigeons.

He said: "We admire the pigeon for its remarkable resilience and individuality.

"People living in cities do not have much contact with wildlife, and pigeons are very important to them.

"Asking people not to feed pigeons is acceptable. But many of the devices used to scare pigeons off result in painful and distressing injuries to the birds."

The dilemma, and the ongoing problem of pigeon control, is one that faces people and organisations of all statures, all over the world.

The Dublin-based company Flock-Off lists London's Savoy Hotel, Macy's in the USA and the South African Parliament in Cape Town among its customers.