FACTORS INFLUENCING NEST-SITE SELECTION, BREEDING DENSITY AND BREEDING SUCCESS IN THE BEARDED VULTURE (GYPAETUS-BARBATUS)

1. We examined the nest site selection, breeding density and breeding success in the bearded vulture Gypaetus barbatus in relation to physiography, climate, land-use and degree of human disturbance. The study area was in the Pyrenean Cordillera, Spain, where the largest European population of this species occurs. Univariate analyses and Generalized Linear Models were employed. 2. Models correctly classified the 78% of the cliffs analysed (occupied by bearded vultures, and selected at random). The probability of occupation of a cliff by bearded vultures was directly related to the ruggedness of the topography, altitude, distance to the nearest bearded vulture occupied nest, and distance to the nearest village. 3. Breeding density was positively correlated with altitude and ruggedness of the topography and negatively correlated with snow precipitation. Open areas seemed also to have positive effects, probably by increasing the availability of food, although its effects were not separable from that of the relief, as the two factors covary. 4. Bearded vultures showed lower breeding success in areas with high potential human disturbance (density of paved roads). The existence of abrupt and open lands might have a positive effect on breeding success by reducing accessibility to humans, and perhaps by increasing food availability.