Function and temporal variation in use of ossuaries by Bearded Vultures (Gypaetus barbatus) during the nestling period

We analyze the use and functionality of ossuaries by the Bearded Vulture (G ypactus barbatus) in the Pyrenees during the nestling period. In 71% of cas es, the ossuary was used to prepare food for chicks, in 11% for storing foo d, and only in 18% for preparing the adults' own food. Pairs used an averag e of two ossuaries at a mean distance from the nest of 789 in (SE +/- 377). The average time dedicate to breaking bone was 5.3 min (SE +/- 4.2) and 4. 5 throws (SE +/- 5.8) for each session in the ossuarie (n = 86). The tempor al variation found in the use of the ossuaries, with maximum frequencies be tween 31-90 days of age of chicks, may be due to a possible qualitative var iation in chicks' diets. Ossuaries are also used to store food, this being a differentiating and advantageous trait with respect to feeding behavior d eveloped by other meat scavengers.