Andy Waters winces on hearing the word “pest”. For the regional spokesman for the RSPB, it is an unfitting label for a magnificent bird of prey, already lost to many parts of Europe.

For him the story of the return of the red kite to the Chilterns is cause for pride. “Everyone should be celebrating what is one of the most successful conservation stories in the world. It’s a shame we are not,” he says.

For what the public, broadcasters and even conservationists have been focusing on over the last year is the story of how a once endangered bird is now so common that it has become a “pest” in the Oxfordshire countryside.

Between 1989 and 1994, 93 fledgling red kites were released in the Chilterns and now it is estimated that there are more than 1,000 pairs in the area and surrounding counties.

But it seems in the blink of an eye red kites have gone from being precious birds of prey, given a new lease of life, to a menace that could spread from the countryside to Oxford itself.

Familiarity can rarely have bred contempt quite so rapidly in wildlife Britain.

There have been reports of unwelcome behaviour, with red kites — with their distinctive forked tails and five-foot wing spans — swooping down in gardens and school grounds, ruining picnics and barbecues.

But it now appears that it is in fact the misguided kindness of humans who have turned a good news story bad by leaving out food.

Both the RSPB and the Chilterns Conservation Board are now making renewed appeals to people to stop feeding red kites.

Conservation Board spokesman Cathy Rose said: “Red kites are now a familiar and much-loved sight over the Chilterns, with many residents gaining great pleasure from seeing them.

“But we believe that red kites are clustering over our villages and coming worryingly close to people and pets because they have become accustomed to being fed. The issue seems to be that the birds are coming into closer proximity to homes than people like.

“They are not aggressive birds, but are merely capitalising on feeding opportunities. They have learnt over several years that an easy source of food can be found close to human habitation, so they are now seeking it out.

“We are being asked whether anything can be done to prevent this unwelcome behaviour. The only way to stop them swooping into schools and gardens is to remove the source of food. Soon they will realise there is nothing for them in that locality and will search elsewhere.”

Ms Rose added that the increasing numbers of kites could easily be sustained by natural food sources available to them in the countryside. Carrion is by far their biggest source of food, with live prey such as rats, mice and voles being a supplementary food source.

“We need to put the message out that feeding is unnecessary. The people who do the feeding, do it for the right reason to help. It’s not illegal to feed kites.

“We must hope that people who are feeding will take heed of the issues of over-population, and consider stopping or at least reducing their feeding.”

Mr Waters said people living near the M40 needed to be reminded just how fortunate they were — because red kites are continuing to decline across Europe because of agricultural practices and deliberate poisoning in some places.

”We now have seven per cent of the European red kite population in the UK — one of the most important red kite populations in Europe, where they still under threat.

“And the great thing is that they are a self-sustaining population. It is easy to forget that a lot of people across the UK will never have seen a red kite. It is such a shame that the debate is still about feeding. We just need people to show some common sense, so everyone can enjoy them.”

The success in the Chilterns has allowed young kites from the area to be moved to new sites around the country and there are now other populations of red kites in mid-Wales, north, sentral and southern Scotland, the Midlands, Yorkshire and Northern Ireland.

Less than two years ago, there was a similar appeal for people in Benson to stop feeding them as it was feared great numbers of them were endangering the helicopters using the RAF base.

By the late 1980s, the species had been absent from England and Scotland for almost 100 years. Many farmers, landowners and gamekeepers had maintained that because they were birds of prey, the red kites posed a threat to smaller game birds, livestock and wildlife. Mr Waters said that even now in other European countries, including even Ireland, red kites continue to be vulnerable to persecution.

Researchers at Reading University are investigating the impact of feeding to establish whether this has led to the large numbers of red kites now seen in urban and suburban areas close to reintroduction sites.

The research involves the UK’s first large-scale questionnaire of people who feed red kites in gardens.

Melanie Orros, of Reading University said: “The red kite is primarily a carrion feeder so will take various types of meat. Little is known about the quantities, types of food and how often people feed them and why. There are likely to be many factors behind the kites’ presence in built-up areas and I’m interested to see if this association with humans might be one that has tipped things in their favour.

“Reading is probably the only large urban area in the UK where large numbers of kites are currently seen. Other reintroductions close to towns and cities has taken place relatively recently. Assuming no mishaps, I would predict that Oxford and other cities close to reintroduction sites will see similar densities in the future.”