Country: Radical action, including the culling of deer, has ensured that endangered birds are thriving in Speyside
We drove out through ancient pinewoood made magical by a slow and wintry dawn. Fresh snow had coated the heather with silver, and through the black canopy of the forest the foothills of the Cairngorms gleamed like smooth, white pillows as they climbed away towards a leaden sky.

No matter that reveille on Thursday had been at 4am. Nothing could damp the anticipation of 30-odd visitors who sallied forth at first light into the 32,000 acres of the Abernethy Forest Reserve on Speyside. Guests of the Royal Society for the Protection of Birds, we set off in small parties heading for 12 separate leks - the open spaces on which black grouse congregate to conduct their arcane mating rituals.

In command of my group was Desmond Dugan, one of the RSPB rangers. As he drove, he described how the blackcocks take up position on grassy patches to display to their females, the greyhens.

Leaving the Land-Rover, we ploughed through snow-crusted heather to a vantage-point under some pines - and there below us business was in full swing. Desmond called the flat area a "green", but the return of winter had made it a "white", and on that pale background 28 hefty black birds showed up perfectly. The alpha, or dominant, cocks were occupying centre stage, as younger birds manoeuvred for position further out.

With scarlet wattles above the eyes, lyre-shaped tails curling outwards at the end, and patches of snowy white feathers splashed about their anatomy, the big fellows were indisputably handsome - but they weren't half making fools of themselves. Strutting, posturing, puffing out the air-sacs in their chests, fluffing up their tail-coverts, they threw dignity to the winds in their efforts to impress potential wives.

Of these, there was scarcely a sign. We felt sure plenty were watching from round about, but we saw only one. Maybe some had been mated already. Maybe it was just too cold for the rest. As Desmond remarked, "Who'd take their trousers down on a morning as cold as this?"

For this Woodland Grouse Management Day arranged by the RSPB, landowners and lairds, farmers, foresters, scientists, bird specialists and others had gathered from far and wide. And by the time we returned to the lodge at 7.30am, we were much impressed. The total of blackcocks seen amounted to 190 - more than four times the number recorded at the first surveys here in 1989.

This rosy picture presents a sharp contrast with developments elsewhere. In every other part of their range, in Wales, northern England and Scotland, blackgame are declining or barely holding their own. In Perthshire, their traditional stronghold, numbers have fallen by more than 50 per cent during the past seven years. Yet on the Abernethy reserve there are now more birds than on all the other 17 sporting estates in the region.

The success is due to the enlightened policy developed by the RSPB over the past 20 years. In buying the estate, the Society's aim was to conserve and if possible expand one of the surviving remnants of the Caledonian forest, which once covered much of the Highlands. Conservation of the forest would, it was hoped, ensure the well-being of its key bird species - among them capercaillie, black grouse, Scottish crossbill and crested tit.

The main threat to the trees came from red deer, which were browsing off seedlings with such efficiency that there was no chance of any natural regeneration. The RSPB therefore took the controversial step of carrying out a drastic cull.

The resulting changes have been spectacular. Not only are seedling pines surviving by the thousand, so that the edges of the forest are creeping outwards on to the flanks of the hills. During the same period, the ground vegetation has become more lush, providing better habitat for black grouse and caper. In many places the heather and bilberry are two feet deep.

Unlike red grouse, which live on open heather moors, black grouse are birds of the moorland and woodland edge, and thrive in a mixture of tree cover and open glades. Adults eat tree-buds and shoots of heather, but in the first few weeks of life their chicks need a high proportion of protein in the form of insects. This makes blaeberry bushes, which harbour caterpillars and other invertebrates, especially valuable.

Another fact established by recent research is that the wire fences built to exclude deer from new plantations are a major cause of mortality among both black grouse and caper. Birds are particularly at risk when they come off their roost in the dark before dawn and glide down to feeding or lekking areas. Experiments have shown that fatal collisions are much reduced if wires are decorated with orange netting to make them more visible. But the best expedient is to remove the fences altogether.

This is what the RSPB has done at Abernethy. In the past few years 25 miles of two-metre-high fences have been ripped out, and it seems certain that the elimination of this major hazard has helped the blackgame recover.

For the past century at least, sporting considerations have been paramount in many parts of the Highlands: deer and deer-stalking have come first, trees a poor second. Now other famous forests - Rothiemurcus, Mar Lodge, Glenfeshie - are going down the Abernethy road, reducing deer numbers and removing fences. In none of these places is the aim to exterminate the deer: rather, the plan is to maintain smaller herds, and to give the trees priority. This dynamic shift of policy should certainly benefit woodland grouse over a wide area - especially if the ideas and methods discussed at Abernethy on Thursday are exported into other estates.

After our early foray, experts analysed the results obtained by the RSPB so far, and outlined possible future conservation initiatives. A talk by Dr Robert Moss, formerly of the Institute of Terrestrial Ecology, emphasised the precarious state of the capercaillie population in Scotland as a whole.

Most people believe that capers became extinct in Scotland during the 18th century; other specialists feel sure that a few birds survived. Either way, fresh stocks were introduced from Scandinavia to Tayside in 1837; and after a slow build-up, they flourished so strongly in eastern Scotland that by the 1920s they were regarded as a menace to forestry.Until the 1970s they continued to do well, but in the past 10 years they have gone into steep decline, numbers falling from 20,000 to barely a tenth of that.

Through catching poults and fitting them with radios, scientists have discovered that young adult caper cover astonishing distances, apparently in search of somewhere to live. Hens, especially, may travel up to 20 miles from their place of birth, and this makes it clear that future schemes for habitat management will have to cover very large areas.

By the time we dispersed from Abernethy on Thursday, everyone had become infected by the enthusiasm with which the RSPB rangers spoke of their charges. If you throw in the fact that, besides black grouse and caper, we saw red grouse, several hundred red deer, golden eagles, curlew, goldeneye and tufted duck, mallard and red-throated divers, you can imagine that we had a pretty good day.