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Abstract

Egyptian vultures were studied during their post-fledging dependence period in northern Spain in order to detect if there were parent-offspring and sibling tensions during the transition of young to independence. The frequency of parental feedings and the frequency of movements of the parents towards their young decreased during the post-fledging period, especially in its final part. At the same time, the frequency of movements and of aggression by the young towards their parents increased. Aggression by adults to their young was not observed. Siblings disputed feedings, but there was no other evidence for sibling conflict. The results suggest that parent-offspring and sibling conflict exists and that its development is broken by the departure of young on migration. Some behavioural traits of adults (maintenance of distance from young and of intensity of nest-defence, tolerance of young during foraging trips through the home range) do not accord with parent-offspring conflict perhaps because they are related to factors other than family tension.