Red kite makes triumphant return in England and Scotland but numbers decline elsewhere

The red kite, the large fork-tailed bird of prey reintroduced to England a decade ago, is booming so much that its population in the Chiltern Hills north-west of London is now believed to be the densest in Europe.

The red kite, the large fork-tailed bird of prey reintroduced to England a decade ago, is booming so much that its population in the Chiltern Hills north-west of London is now believed to be the densest in Europe.

Nearly 150 pairs are nesting in the undulating beechwoods along the Chiltern ridge from Goring in Oxfordshire to Luton in Bedfordshire, new figures show, and the bird is now a regular and spectacular sight along the M40 motorway which cuts through the Chiltern escarpment at Aston Rowant, between High Wycombe and Oxford.

A carrion feeder and once a scavenger on London's streets (and mentioned as such in Shakespeare), the red kite became extinct in England in 1870, and in Scotland in 1890. For most of the 20th century the remoter parts of mid-Wales remained its only stronghold.

But in the late 1980s the decision was taken to reintroduce it to England and Scotland, using birds from Spain and Sweden, and the project has turned into one of the most successful bird reintroduction programmes ever seen.

From having no birds in 1989, England had 177 pairs nesting last year, while Scotland had 50. In Wales, although no survey was carried out last year, it is thought that between 300 and 350 pairs are nesting. The English birds consist of 142 pairs in the Chilterns, 25 pairs in Northamptonshire and a further 10 pairs in Yorkshire.

The full British population of between 500 and 600 pairs, still steadily expanding, is now regarded as the healthiest in Europe, according to the Royal Society for the Protection of Birds. Other red kite populations, such as those in Spain, France and Germany, are declining, or at best stable.

The concentration along the Chiltern ridge is now probably Europe's densest, said the RSPB's Graham Madge. "The breeding success is really unprecedented."

So common have these birds become that it is rare to drive down the great chalk cutting where the motorway bisects the Chiltern ridge, and not see one. On the M40 they have replaced the kestrel as the common bird of prey.

Drivers should look out for a large bird with a noticeable forked tail, soaring in flight, or slowly flapping long wings with white patches and finger-like feathers projecting at the end.

The Chiltern birds have probably done so well because of an ample supply of tall trees for nesting and thermals the birds can use to soar on to spot the dead animals on which they feed, Mr Madge said.

However, both the RSPB and English Nature, the Government's wildlife agency, are sounding a warning about the dangers that new rat poisons can present to birds of prey, and kites especially, because of their carrion feeding.

A new leaflet spells out the dangers from so-called "second generation" rodenticides, based on anticoagulants, which can persist in the bodies of dead vermin.

Red kites will eat poisoned animals that died in the open and several birds from the reintroduction project have been killed in this way in England and Scotland in recent years. The leaflet gives guidance on how to minimise risk to birds of prey when undertaking rodent control. Other once-scarce large birds of prey, besides the red kite, appear to be doing quite well in England. Honey buzzards, goshawks and marsh harriers all have robust populations now.

In Scotland, the reintroduction of the white-tailed sea eagle to the Hebridean islands is also going well, with several pairs breeding – but nowhere near on the scale of the red kite.