Rarely seen but never forgotten, it is reckoned to be one of the natural wonders of the moors. Nick Morrison goes in search of the elusive lekking of the black grouse.

ANYONE who knows anything about moorland birds will tell you it is one of the most impressive spectacles to behold. None who see - and hear - the performance can fail to be impressed, particularly considering it is by one of the rarest, and shyest, of creatures.

So it was that I found myself at 5.30 on a damp and misty morning on the top of Barningham Moor, a few miles south of Barnard Castle in County Durham - lured by the prospect of seeing the lek of the blackcock.

To those blissfully unaware of this natural curiosity, lekking takes place between March and May and is an attempt by the blackcock, the male black grouse, to impress the females, naturally called greyhens. The blackcock do this by puffing out their plumage and dancing around, much as another more familiar species is sometimes known to do.

But it is not only this which singles the blackcock out for special mention. Just as impressive - hopefully to the greyhens as well as to us - is the musical accompaniment. As imitated by Roy Burrows, my guide for the morning, it consists of a drawn-out "kweeoch" kind of noise, followed by a throaty warble. Apparently, when a number of blackcock perform simultaneously, it provides an eerie orchestral soundtrack to the moorland vista.

I meet Roy at Barningham Park, home to Sir Anthony Milbank. Sir Anthony, a former chairman of the Moorland Association and still a committee member, has made conserving the blackcock a key element in the management of his land. Roy has been the head keeper on Sir Anthony's 6,000-acre estate for nine years. His father was a gamekeeper, and it seems what Roy doesn't know about the moors probably isn't worth knowing.

Unfortunately, one of the things he knows is that today isn't likely to be a good day for lekking. Yesterday was perfect, the day before was also excellent, even the day before that, when we had been due to meet but postponed after a gloomy weather forecast, would have been good. But today it is drizzling, and apparently the blackcock don't like the rain.

But it's 5.30am and I'm not about to turn up this early any other day, so we head off for the moors.

After reaching the top of the moors, we park the 4x4 by the side of the road and start walking down a track into the heart of 300 acres which, for the last ten years, has been under stewardship, meaning instead of being intensively farmed, it has been managed to provide a variety of natural habitats.

Black grouse, perhaps boring easily, like to have varied surroundings. A few trees to perch in, a bit of long grass to root about in, a bit of heather to hide in, perhaps boggy patches for sloshing about in and solid ground for drying off.

"They have got everything within the vicinity here. They're known as being a bit of a moorland fringe bird, so this is ideal country for them," Roy says.

We stalk quietly towards the lekking site, secreting ourselves in the corner of a field behind a dry stone wall. Roy points towards a clump of long grass about 50 yards ahead, where it is possible to make out three or four little black bird-shaped heads. We wait for a few minutes but there doesn't seem to be much lekking going on. They may love performing in front of their mates, but it seems the presence of strangers has made them come over all shy.

As we watch the barely-moving heads, in a whisper Roy explains to me the ritual of lekking.

"It is to show who is the most attractive cock, and who will get to service the hens. They puff out their feathers but they don't fight, they just sort of dance around. They will all be together in a big circle, doing a big tribal dance, and they're all trying to outdo each other. It seems to be the biggest and brightest who work their way into the middle, but it is often a different one each time.

"The others feel a bit overpowered and subdued and disappear, although there is never just one left in the middle. And often there is one who has been knocked out who sneaks around the back to service the hens."

This seems a little unfair on those who are still on the dancefloor, presumably in the belief that it could be their morning, but the hens, who watch from a respectful distance, don't seem to mind that they're getting one of the losers.

The rest of the day the cocks hang around together - "like they're out with the lads" says Roy - and the hens keep to their groups. Needless to say, once the chicks are born, the cocks don't want to know.

Roy says he has seen up to 14 cocks on the lekking site, and around eight hens, though they are more reclusive and harder to spot, and don't turn up every day. Presumably some days they just don't feel like it. Upper Teesdale is home to around 140 displaying blackcock, about a fifth of the remaining English population of a bird whose numbers have declined alarmingly over the last 50 years.

Disappearing habitats and an increase in predators, chiefly foxes and crows, have seen the black grouse put on the 'red list' of birds in greatest need of conservation, declining at the rate of ten per cent a year.

Numbers in Teesdale have largely remained stable, thanks to strenuous efforts to maintain and enhance their habitats, but their breeding rate is just enough to keep the population stable. Last year, eight chicks were spotted, four the year before and none at all the year before that.

But the rain seems to have dampened their ardour this morning. Or perhaps the wind is in the wrong direction, so we abandon our position and try it from another angle. Manoeuvering the 4x4 gingerly along a bumpy track across the moorland, we approach from the other side. We come to a stop, again about 50 yards from the lekking site, but this time there does appear to be some activity.

Four males are in front of us, doing their little jigs and puffing up their feathers. And, ear cocked to the wind, I can just about make out the "kweeoch" noise, although there is no hint of a warble. Another two join them, and the six of them take turns to dance and "kweeoch".

One by one, they gradually disappear into the long grass, perhaps in some sneaky attempt to score with the hens, who are apparently lurking in the vicinity. After a few minutes, they have all gone, and we are left looking at a few tufts of grass, with not even a rustle to hint at what might be going on.

As we depart, Roy tries his best to console me. "That was a bit of a half-hearted attempt at doing it, but when they all start and they get going the noise is amazing. You can just stop on the road and hear them - they're all making that cracking noise and then the warbling. You haven't really seen them at their best," he says. That's a great comfort, as I head back in the drizzle.