Nest-building behaviour of the Bearded vulture Gypaetus barbatus

Bearded vultures Gypaetus barbatus began supplying material to their nests on average 111 d (range 91-126 d) prior to laying. Males were significantly more active that females. Heavy material (branches) was transported indistinctly in the talons or in the bill while lining (wool) was generally transported in the bill. 71% of the wool was recycled from remains fallen from other nests, probably due to the scarcity of this material in relation to its importance for insulating the egg and chick from the low winter temperatures. No inter-sexual differences were observed with regard to the type of the material selected or how it was carried to the nest. The early nest-building behaviour and the fact that the males were the most active builders are discussed in the context of maintenance of the pair-bond and female selection. After laying, material for nest-maintenance was only rarely supplied, suggesting high solidity of the structure at its location at protected sites.The study was jointly financed by the Departament d'Agricultura Ramaderia i Pesca of the Catalonian Autonomous Government (Generalitat de Catalunya), Fundació Territori i Paisatge, Minuartia Estudis Ambientals and the Life Fund of the European Union (Life Project 94/E/A221/E/01126/ASJ)Peer reviewe