Malcom Smith goes hawk hunting in the Pyrenees
We drove for miles along a tortuous track in the Riu Joeu valley, mesmerised by the colours and texture of the fir and birch forests. Then we walked. We had come to this part of the Pyrenees, west of Andorra, to see the bone-breaker - so named because of its habit of flying skyward with a sheep or goat bone, and dropping it on to rocks to break it open for a meal of the marrow. Also known as the bearded vulture, or lammergeier, it has a wing-span of up to 9ft, a steel grey back, orange underparts and an orange head with black facial markings. Lammergeiers are unmistakable. Although they are rare in Europe, there are more than 70 breeding pairs in the Pyrenees. So we felt they should be easy to find ...

According to local experts, it's quite possible to see them gliding along almost any valley, usually high up near the mountain tops, searching for an animal that has recently expired in the unforgiving terrain. So our first attempt, albeit with low cloud from the previous night's thunderstorms clearing slowly through the day, took us along a side valley off the main Vall d' Aran, with the Garonne river cleaving down its middle.

Passing typical Aranese buildings of stone with steep, slate roofs, we walked for several miles on tracks and paths, by turbulent streams through forests of lichen-draped spruces, black pines and birch. Jays shouted their harsh calls, like rough gearboxes in the trees. Apollo butterflies the size of small birds fluttered around. Stunning little black-and-yellow fire salamanders plodded across damp footpaths. But nothing resembling a lammergeier came into sight all day.

Undeterred, the next day we decided to head for what is arguably the most isolated part of the Pyrenees, the Aigues Tortes and St Maurice National Park. Catalonia's only national park, it covers 130 square kilometres of rugged mountain land, with forests and snow-capped peaks rising to 10,000ft. Since almost all of it is publicly owned, the park has no habitation and imposes strict controls on vehicles. It is a mountain walker's dreamland.

To get into Aigues Tortes, there are three approaches by road, via the small towns of Boi to the west, Capdella at the head of the Flamicell river to the south and - the way we used - Espot to the east. We hired what's called a "Jeep taxi" (in fact a nine-seater Land Rover) from Espot (they line up a few yards from the national park's information centre), and drove about eight kilmetres to the picturesque St Maurice lake. At weekends this is a honey-pot. Yet on weekdays some of the hiking trails are surprisingly underused. We walked up the Monestero valley to the south of the lake. It turned out to be an inspired choice. Under the silver firs, Norway spruce and Scots pines, alpenrose bushes carpeted the ground between the boulders. Wetter ground beside the thunderous Riu Monestero stream shone with pink marsh orchids and the apple-white flowers of grass of Parnassus. Shady corners behind boulders grew fern gardens and all around were butterflies coloured white, blue, deep yellow, orange - and even all black.

Sitting above the little Monestero lake amongst the alpine meadows speckled with blue scabious and 2ft-tall yellow gentians, with boulder-strewn slopes and high cliffs tiered above the valley sides, we thought it seemed the perfect hunting ground for a lammergeier. For hours we scanned and rescanned with binoculars, hoping, hoping for the telltale dark vulture wings, the wedge-shaped tail and the orange belly. But it was not to be.

So, one more try. This time in a steep-sided valley, part forested, part grassland, south of Vielha.

"Many times here I have seen lammergeiers drop bones of sheep or goats," said Toni Margalida, an expert on the species who has been monitoring them in this part of the Pyrenees for 10 years, and had joined us for the morning. He pointed past the high cliffs and forested slopes to a boulder scree perhaps a couple of miles away. Hereabouts, so the experts said, lammergeiers often patrol the hillsides looking for dead animals.

One hour went by, then two. Griffon vultures appeared, their huge, light- brown wings keeping them aloft on the updrafts. A golden eagle did much the same. Even a brown-and-white short-toed eagle (it beats me to understand how anyone gets close enough to see such anatomical detail), perched nearby on an electricity pole.

Then came the cry we had waited nearly a week for.

"Lammergeier!" shouted Toni, almost as excitedly as if he, too, was seeing the bird for the first time. And there it was, through the binoculars and telescopes, a text-book image of a bone-breaker in flight: head down, wings held outstretched and still as it glided this way and that, rather ominously, above a huge flock of sheep being closely shepherded on high Pyrenean pastures.

As it glided closer, patrolling the steep cliffs above hanging forests, the orange-coloured chest and head - with the fearsome black beard markings - became more and more obvious. The same size as the griffon vultures hanging in the air high above the mountain peaks, lammergeiers somehow look far more purposeful; more majestic, too.

It's a fitting bird for such a splendid mountain range. The long wait had been worth it.

The closest international airport to Vielha is Toulouse, across the border in France, but it is cheaper and easier to approach the area from Barcelona. EasyJet (01582 445566) has a return fare of between pounds 103 and pounds 153, with no restrictions; lower fares sell out first. From Barcelona, there is a daily bus to Vielha, taking around four hours. Information on the Aigues Tortes National Park can be obtained from the Park's administration at Calle Camp de Mart 35, 25004 Lleida (00 34 73 246650). Spanish National Tourist Office: 57 St James's Street, London SW1A 1LD (0171-499 0901).