Esher's 6,000-strong population parakeets may have to be culled to save native species.

It is believed the exotic birds are responsible for a decline in native British birds such as the robin, nuthatch and the starling - whose numbers have dropped more than 60 per cent in the last 25 years.

Last week the Department for Environment, Food and Rural Affairs (Defra) commissioned a laboratory to undertake a study of the birds, and Defra also say they are working with bird societies to understand the true nature of the problem.

Because they nest in January, long before other native birds, parakeets leave fewer tree-holes for other birds to nest in. A cull appears to be the likely solution.

A flock of 6,000 parakeets roost at Esher's Rugby Club and well over 30,000 are believed to nest in Britain, mostly in the south east.

Attractive and elegant, the birds have rarely been considered a problem, but nature expert Tony Drakeford warns action is needed quickly as their numbers are predicted to rise to 50,000 in three years.

He said they were a very invasive bird and likened them to the problem of Japanese knot-weed.

He said: "There is not an ecological niche for parakeets in Britain and they are upsetting a fragile ecological balance that has taken thousands of years to form."

He said numbers needed to be cut before the birds spread further north and west, but any cull would not be easy. The birds prefer to roost in tall trees so access to pricking eggs is limited, and gassing or netting could kill other species.

Mr Drakeford said: "I can't think of any sensible solution. It's a very difficult situation."

Land owners can apply to conservation agency Natural England for a licence to control the birds, either for conservation, to protect crops or to protect public health and safety.

A spokesman at the agency said a one month licence had been granted to an unnamed site in Esher to kill up to 30 birds. Issued to protect crops the licence was issued as "shooting as an aid to scaring".

A spokeswoman at Esher Rugby Club, which has named its girl's under-17 team ater the birds, said they were a mixed blessing - very attractive but very noisy.

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