Territorial defence and agonistic behaviour of breeding bearded vultures Gypaetus barbatus toward conspecifics and heterospecifics

Abstract

Territoriality and agonistic behaviour against conspecifics and heterospecifics was recorded for nine breeding pairs of bearded vulture Gypaetus barbatus between 1992 and 1996 in the Pyrenees (NE Spain). For both sexes, the defence intensity increased from the pre-laying to the chick-rearing period. The intensity of nest defence was significantly higher in males during the pre-laying period but no sex differences were found during the incubation and chick-rearing periods. Competition for nest sites, food and the potential risk of predation may affect the bearded vulture's nest defence behaviour towards other species. Most agonistic interactions took place against Eurasian griffon vultures (the most abundant species and the most important competing for nest sites) and common ravens (the most likely potential predator and a kleptoparasitic species). Nest defence against conspecifics mainly took place during the pre-laying period and may be linked to sperm competition and food resource competition.