It is one of the country's most celebrated singers, but now fears have been raised that it's song may disappear forever.

Populations of the nightingale, known for its distinctive song and revered in literature for generations, have declined by 50pc across the UK since 1998, even in previous strongholds like Norfolk and East Anglia.

In Bradfield Woods in Suffolk, for example, numbers dropped from 12 pairs seven years ago to two, one year ago, and none remainin now.

It is unclear exactly what is to blame for the fall but researchers at the British Trust for Ornithology (BTO), based in Thetford, believe it is likely to be pressures in breeding areas in the UK, on migration to and from Africa, and within wintering areas south of the Sahara Desert.

Research ecologist at the BTO, Chris Hewson, said: 'Some of it is to do with woodland here and some with what's happening in Africa. The woodland has changed quite a lot because of grazing. Muntjac deer in particular have increased.

'The nightingale nest quite low to the ground and feed from the ground but they sing from the trees. All woods have got canopy but not all have got vegetation that's sufficiently dense at the bottom. Things are also changing in Africa which is where they spend their winter.'

To find out more, a survey of nightingales is planned for 2012 as well as further work looking at its habitat, both in the UK and Africa.

The BTO has already tracked one nightingale to Africa and back successfully, using geolocators, and hope to carry out more work on this to gain further insights into the nightingale lifestyle.

Between 2009 and 2010 the bird was tracked from Methwold Hythe in west Norfolk to Senegal and Western Guinuea, a distance of more than �1,000 miles, and it is hoped by learning more about habitats both in Africa and at home the decline can be halted.

The BTO's first task would be to record the distribution of the nightingale, how many are paired, and where they return to. The team would also carry out detailed work on the ecology of Africa.

Mr Hewson said: 'It's extremely important because without stopping this we could see complete extinction of them. Even a reduction in numbers is significant because they are an important species.

'There are lots of references in literature and people come a lot to hear them sing. People love to hear them so it would be a huge blow to the countryside to lose them. They're also important in their own right because they're a large long-distance migrant which is quite remarkable given their size. They're one of the largest migrants at 20g.'

The BTO has launched the Nightingale Appeal and a CD of the bird singing to the backdrop of world war II bombers over southern England, and Beatrice Harrison playing her cello accompanied by a singing nightingale, is now on sale. This is the first recording of a wild bird or animal not in captivity and the profits will fund research into its decline.

To order a copy call 01842 750050, or visit www.bto.org/nightingales. Donations can also be made in this way.