Shakespeare's red kite returns to London after an absence of 150 years

Once it was as much a London bird as the ravens in the Tower of London. The streets of Shakespeare's capital were full of red kites. "The city of kites and crows," he calls it.

Although magnificent in appearance, the birds were scavengers, never short of a meal at a time when people threw their rubbish in the street. They also stole washing off lines for their nests, and Autolycus, the streetsmart conman in A Winter's Tale, warns: "When the kite builds, look to lesser linen."

But gradually improving public hygiene and waste-disposal robbed the red kite of its niche in the London ecosystem, and by the end of the 18th century it was extinct as a breeding bird. The last sighting on the streets of the capital was in 1859. Until this week.

Michael Croft, who lives in Hackney, east London, was amazed at what he saw outside his back door. "I heard an awful commotion and saw these great wings; it was huge," he said. "It was being chased by crows and magpies. It was crazy, like a scene from an Alfred Hitchcock film. I know buzzards get mobbed by birds so I realised what was happening. At first I thought it was an eagle and called police."

The kite's appearance marks the most striking advance yet in the bird's return across the country in the past 15 years, in what has been the most successful wildlife reintroduction programme Britain has experienced.

For most of the 20th century, red kites were absent from all of the country except for central Wales, where a about 40 pairs stubbornly clung on, helped by dedicated volunteers who guarded the nests from egg-collectors. The first Welsh kite protection programme started in 1903 and is the longest continuous conservation project in the world. But in 1989 British conservationists began an ambitious scheme to reintroduce Milvus milvus to its former haunts, using a few young Welsh birds, and more from Sweden and Spain.

The release of 93 birds in England and Scotland between 1989 and 1994 proved a spectacular success. The first breeding was in 1992 and the population has mushroomed, especially in the Chiltern Hills north-west of London, the wooded slopes making perfect breeding territory. In 2004, out of an estimated total of 836 red kite breeding pairs in Britain, there were 215 nests in the Chilterns, out of an English total of 276. (The other English breeding centres are in Northamptonshire and Yorkshire.) The Welsh population was up to 500 pairs, with 60 breeding pairs in Scotland.

In 2005 there were probably nearly 1,000 pairs nesting, although no accurate figure is available, because they have spread so far. The Chilterns birds can be seen along the M40 from London to Birmingham, a spectacular sight with their five-foot wingspan and deeply forked tails. The kite Mr Croft saw in a Hackney back garden was almost certainly a Chilterns bird. "It was totally cool," he said. "It didn't bat an eyelid. I took my daughter with me and we looked at it for about five minutes before it flew away. It was beautiful."