The Ossau nature reserve protects two sites made of cliffs and masses of fallen limestone rocks on the right bank of the Ossau valley, covering a total surface area of 82.3 ha.
The reserve was created in 1974 on the initiative of environmental protection associations and thanks to the support of villages owning the land: Aste-Béon, Bielle, Bilhères and Castet.
The main objective of the nature reserve is to encourage the reproduction of the colony of griffon vultures.
It is managed by the Pyrenees National Park that also keep a daily watch over it during the nesting period (December to September).
The rules forbid in particular all entry during this period and ban flights over the reserve all year long, even hang gliding and paragliding.
The following figures sum up the success of the Ossau nature reserve:
Upon its creation:
10 breeding pairs and 7 flying chicks
105 breeding pairs and 32 flying chicks
2008: 84 breeding pairs