A dance of defiance in the black grouse's stronghold

In the dawn light, the pure white blob is visible from a quarter of a mile away on the grey-brown moor. It is a bird's backside. It is a backside of quite remarkable magnificence.

In the dawn light, the pure white blob is visible from a quarter of a mile away on the grey-brown moor. It is a bird's backside. It is a backside of quite remarkable magnificence.

It belongs to a male black grouse, one of Britain's most rapidly disappearing birds, and it is being stuck up into the air in a provocative manner, somewhat like the Scots soldiers mooning at the English army in Mel Gibson's Braveheart.

But it does not say, the hell with you. It says, Hey. Look at me, guys. Ever see a backside quite like that? Huh?

The bird on the moorland is at its "lek" – its display ground, its catwalk, its disco dancefloor – and it is strutting its stuff in the activity that is all-consuming in the black grouse world, attracting a mate.

It is being joined by several other males, and blow me but what do they do as soon as they land but stick their own under-tail-coverts – to use the technical term for that pure white derrière – up in the air too.

Then they circle around each other warily, advancing and retreating, bobbing and weaving, all the time making a strange low bubbling sound which carries clearly through the still air of the early morning.

It is 6.50am, high in the Welsh hills, and watching these increasingly rare but stunningly beautiful birds perform their peculiar display is so compelling that you are unaware that the wet heather you are lying in with your binoculars has soaked you through.

The black grouse lek is one of nature's great spectacles, but it is one that not many people ever see, and it has been getting even less visible. Black grouse numbers have taken an enormously steep dive in the past 10 years and the total in Britain may have dropped from 25,000 to as few as 6,500 displaying males.

Although a game bird, it has long been appreciated by twitchers as well as shooters. It is far handsomer than its cousin the red grouse, with glossy dark blue plumage in the males crowned with a bright crimson eye-comb, and black lyre-shaped tail feathers surmounting that magnificent white backside. It was a favourite bird with the Victorians for stuffing and mounting in glass cases.

But it has completely gone from its old haunts on Exmoor and Dartmoor and the Peak District, and is now confined to the Northern Pennines and Scotland – with its remaining southern stronghold in Wales. Yet in Wales too the decline has been steep: Welsh numbers of the bird fell from 264 to 131 males between 1986 and 1997. And five years ago it was clear the black grouse in the principality was on the high road to extinction.

The fact that Tetrao tetrix can still be seen at the lek on the Welsh hills is down to a remarkable piece of conservation: the black grouse project of the Royal Society for the Protection of Birds. The RSPB persuaded a group of substantial donors including the European Union, Forest Enterprise, the Countryside Council for Wales and the Welsh National Assembly to cough up more than £500,000 for an ambitious habitat management programme to encourage the birds to breed.

With much time and effort, hundreds of acres of pine forest edges have been thinned, and hundreds of acres of heather have been partly ploughed, to provide ideal nesting and feeding conditions. The results have been outstanding: on the six best sites that held 80 per cent of the Welsh birds in 1997, numbers are back up above 170 breeding males.

"Lots of different causes have been driving the decline," says the RSPB's black grouse project officer, Pat Lindley.

"In some cases it is the fact that the conifer plantations of the 1950s, which the birds like when the trees are young, grow so much that the canopy closes and there is no vegetation underneath. The birds can linger on for years and years, but then sometimes the last few suddenly disappear."

Mr Lindley has marked a steadily increasing number of leks since the project began, with the one he showed The Independent being particularly prominent.

It is a flat area of rushes in the middle of the moor where the males assemble to display; as the spring goes on they get more and more aggressive until they fly at each other like fighting cocks, the object being to get into the centre of the lek. Females assemble nearby and the bird in the centre is the one they will want to mate with.

Lekking (the word is of Swedish origin) is observed in a few other birds such as ruffs, which are waders, and capercaillies, which are grouse relatives.

The moor we are on was once the prime grouse moor (for red grouse and shooting) in all of Wales; in 1912, a total of 7,142 birds were shot on it.

Now the shooting has finished, and the black grouse are the interest. They fly into the lek in a striking flash of black and white; they puff themselves up and they prance and they dance; they fill the air with their strange bubbling calls. You can't take your eyes off them.

Pat Lindley smiles. "How can you let a bird like that go extinct?" he says.

With such a performance, such glossy blue breast feathers, such elegant tail feathers, such a striking red eye-comb and most of all such a fantastic white backside, visible a quarter of a mile away, how indeed can you?