Résumé :
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Encounter rates between bird predators and three types of flocks in a West african primary rain forest were found to be very different. Hawks potentially dangerous for birds were recorded attacking or approching feeding assemblage of frugivores 7,5 times more often that single species groups and 32 times more than mixed flocks of insectivores. The formers seemed the most attractive to predators and the less adapted to predators avoidance because of their origine and structure, but their vulnerability was offset by feeding advantages. On the contrary, the latter, in spite of their increased conspicuousness over solitary birds, could have a strong deterrent effect on hawks experiencing too low success rates when attacking thme because of effective defence behaviour and vigilance. This stricking antipredator function may be their main advantage. Fear of predators has obvious consequences on the biehaviour of large frugivores and thus on seed dispersal patterns. Résumé d'auteur
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