It is not what you would expect to hear in the Conservative suburban heartlands of Beckenham, Bromley and Boreham Wood in south-east England – homeowners voicing their approval for a wave of immigrants from Asia.

As one of the senior researchers studying the flocks of Afro-Asians said: “Many people say they bring an enormous sense of wellbeing. They say they are charismatic, beautiful, exotic. They absolutely love having them around.”

These immigrants are not human. They are Psittacula krameri, members of the parrot family better known as ring-necked or rose-ringed parakeets.

Their flashing green plumage and shrill squawks have long been part of daily life around the parks, golf courses, university campuses and garden feeding tables of south and west London.

Now they have spread way beyond the M25 and M2 that once marked the extent of their presence in Britain. But if government scientists act on advice they are about to be given by parrot experts, that spread could be halted by the culling of flocks that settle in new sites.

The parakeets are a potential threat to crops and native birds. A four-year European research programme called ParrotNet is about to present its findings to scientists at the Department for Environment, Food and Rural Affairs, one of whom has the perfect name for the job – Dave Parrott. The co-founder of ParrotNet, Hazel Jackson, said the parakeets were “an urgent economic, societal and environmental problem”.

The squawkers are now making a noise in Milton Keynes, Sheffield, Manchester, Liverpool and the Edinburgh-Dundee area. In Europe, parakeets have settled in more than 100 cities, and are found as far north as Estonia and Sweden. They are said to be “out of control” in Brussels, have taken hold in Paris and Amsterdam, and in Spain another species, the monk parakeet or Myiopsitta monachus, is causing problems in Barcelona, Madrid and Seville.

Monk, or Quaker, parakeets, which originate from South America, have settled in Britain too, in Boreham Wood and the Isle of Dogs, but have never numbered more than 100 and are now down to about 50 after a state-approved cull.

Scientists estimate the European parrot population at “a minimum of 85,000” but because they are spreading and breeding so quickly there could be many more than that figure, and there will certainly be in the future. There were an estimated 32,000 ring-necked parakeets in Britain at the last count in 2012.

“There is a potential for parakeets to cause a lot of economic damage, especially to fruit farms and vineyards,” said Jackson, who works at the University of Kent. “There have been problems around the Mediterranean and especially in Israel, where crops have been decimated by parakeets. The birds threaten local biodiversity as they chase away native birds from food sites, and exclude endemic birds and bats from nesting cavities. But people love them. Public perception is a big challenge.”

Sarah Crowley, another ParrotNet expert based at the University of Exeter, has just published a paper that could help to shape government policy. She suggests that decision-makers should “try to address people’s concerns before initiating control projects” and give people a say in the policy-making process.

The worst damage by non-native parakeets has been in Israel, where Yoav Motro, head of the Israel ministry of agriculture’s plant protection service, said: “We have had parakeet problems for decades now, and unfortunately when it comes to numbers and damage, Israel is well ahead of Europe.” Hundreds of parakeets will descend on fields of almonds, sunflowers, pecans and other crops. Losses were hard to quantify, Motro said, but with farmers operating on a 10% profit margin they could lose all their profit to parakeet damage.

Between 1984 and 2007 nearly 150,000 parakeets were imported as pets into Europe. The release of many ring-necked parakeets from captivity, and their ability to thrive in urban areas and cope with low temperatures – they originate from the Himalayas region – has led to their rapid rise in numbers.

“All the populations across Europe have seen the same pattern of exponential growth,” said Jackson. “Populations can double in size within a few years.”

The findings of 25 to 30 core scientists on the ParrotNet project, backed by EU scientific research funding, will be revealed at a conference in September. Before then, policy advice will be sent to Britain’s Non-native Species Secretariat, a state agency that will report to Defra. Jackson said ParrotNet’s recommendations would be:

■ Stricter legislation on the possession, transportation and commercial trafficking of invasive parakeets, which has already happened in Spain.

■ A new system for relinquishing unwanted pet parakeets.

■ Removal of legal and financial constraints on rapid-response eradication of new populations, especially in areas where they are currently not present.

■ Raising public awareness of the parakeet population and potential problems.

Leaving parakeets free to move and breed is an option favoured by the ecologist Chris D Thomas, however. The University of York professor argues against “irrational persecution” of non-native species in a new book, Inheritors of the Earth, to be published this week.

Thomas, who does not agree with the accepted wisdom that humans have irrevocably damaged the natural world, said: “We do not try to control species because they moved in the past, so why should we now try to police the distributions of species that are thriving in the human epoch? It makes no sense.”

Rats, rabbits and hares were “invasive” species to Britain at one time. In the United States, eight pairs of sparrows in 1850 have now become 150 million birds, with no known ill effects on the environment or the economy.

“If parakeets cause a specific problem in a specific location, we may need to control them, or preferably discourage them,” said Thomas.

“Defra should only control them in specific locations, not generally, if there is clear and evident commercial harm, and not because of some misplaced distrust of ‘foreign’ species. Judge a species by its impacts, not by its origins.”

Parakeet influx



Parrot facts

Where do they come from?

Ring-necked parakeets from the Himalayas region and Africa; monk parakeets from South America.

How did they get to Europe?

In the UK, there are several theories about ring-necked parakeets being released during the filming of The African Queen in Shepperton in 1951, or by Jimi Hendrix when he let a pair go free in London in the 1960s. Others say the 1987 storms damaged so many aviaries that many parakeets escaped. A pair were first recorded as having bred in the wild in 1855, and sightings have been steadily growing since the 1930s. Nearly 150,000 were imported into Europe as pets between 1984 and 2007, with many people releasing them from captivity.

How many are here?

Probably 100,000 or more throughout Europe. The latest official figure is “a minimum of 85,000” in Europe, but no detailed recent count has been made. The UK estimate was 32,000 in 2012.

What do they eat?

They like fruit, nuts and seeds but are wasteful eaters, pecking at part of an apple, then moving on to the next one.

Where do they live?

They nest in holes in trees, and thrive in areas of parkland, close to urban homes. Ring-necked parakeet hotspots are Ramsgate, inside the M25, central London parks, Amsterdam, Brussels and Paris. Monk parakeets thrive in Barcelona, Madrid and Seville.