A possible slender-billed curlew was spotted in Suffolk in 2004
A quest to find one of the world's rarest birds, the slender-billed curlew, has been launched by the Royal Society for the Protection of Birds.
The bird has not been sighted definitely for nearly a decade, but researchers hope that a few survive.
The RSPB is funding a hotline and a search team based in the UK.
Satellite technology will be used to track the birds back to their nesting sites in central Asia if any of them are found.
The slender-billed curlew is described as the size of a crow, with delicate brown markings, an extremely slim bill, and a strange whistling cry.
Conservationists admit that with no confirmed sightings this millennium the chances of finding the bird are slender, but they hope that isolated populations may have survived.
Ornithologists say the slender-billed curlew was once a relatively common bird, migrating from its remote breeding grounds in central Asia. Most spent the winter in north Africa and the Middle East.
It is thought hunting has contributed to its dramatic decline and one of the last confirmed sightings was in Northumberland in 1997.
An unconfirmed sighting was reported at Minsmere nature reserve in Suffolk in 2004.
Nicola Crockford, chairwoman of the RSPB's slender-billed curlew working group, said: "Although the situation for the slender-billed curlew does look gloomy, the fact that other species have risen from the "dead" recently does fuel our optimism. We are encouraging people not to give up on this bird."
She added: "Additionally, this bird was known to inhabit remote areas - so it is just possible that small numbers of the bird may still be wintering in an isolated part of north Africa or the Middle East, or that some unknown nesting site may be discovered in the depths of central Asia. But our quest is definitely a race against time."
In 1994, the slender-billed curlew population was estimated to be between 50 and 270 but the lack of recent confirmed sightings suggests it may now be less.