Breeding biology and success of the Bearded Vulture Gypaetus barbatus in the eastern Pyrenees

We present data from an extensive study of Bearded Vulture Gypaetus barbatus breeding biology in the Pyrenees from 1992 to 1999. Average laying date was 6 January (range 11 December to 12 February, n = 69) with no significant differences between years. Eighty per cent of clutches were of two eggs (n = 20) and average incubation was 54 days (range 52-56, n = 14). Hatching occurred on average between 21 February and 3 March (range 5 February-7 April) and the first and last chicks fledged in 21-27 May and 20 July, respectively. The average chick age at fledging was 123 days (range 103-133, n = 20). Bearded Vulture density increased significantly during the study period. Breeding success and productivity declined apparently as a consequence of the increase in the percentage of breeding failures during incubation and chick rearing, most during the hatching period. The factors that may determine breeding failure and the decline in breeding performance are analysed and management recommendations for more effective conservation measures are discussed.