France, Oct. 19 -- In a hidden valley in the French Alps, conservationists are quietly raising Europe's largest bird of prey - the bearded vulture - once wiped out from these mountains. After a century away, it is once again soaring again over the Alps, but its comeback still depends on human care.

Up a steep track above the village of Sallanches in the Arve valley, the road turns to rock and tree roots. Beyond the beech trees, a meadow opens on to a view of Mont Blanc and the Fiz and Aravis ranges. Nestled here is the Asters breeding centre, a small conservation site that has worked since 1986 to bring the bearded vulture back to the Alps.

Its exact location is kept secret. The birds are extremely sensitive to stress - it can even kill...