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 (Gypaetus barbatus) in the Pyrenees during the nestling period. In 71% of cases, the ossuary was used to prepare food for chicks, in 11% for storing food, and only in 18% for preparing the adults' own food. Pairs used an average of two ossuaries at a mean distance from the nest of 789 m (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 temporal variation found in the use of the ossuaries, with maximum frequencies between 31-90 days of age of chicks, may be due to a possible qualitative variation in chicks' diets. Ossuaries are also used to store food, this being a differentiating and advantageous trait with respect to feeding behavior developed by other meat scavengers.This study was supported by Departament d'Agricultura Ramaderia i Pesca of the Generalitat de Catalunya, Fundació Territori i Paisatge, Minuartia Estudis Ambientals and a Life Project of the European Union (94/E/A221/E/01126/ASJ).Peer reviewe