Juvenile and adult behaviour was studied at eight nests of Black KitesMilvus migranswithin the Doñana Biological Reserve, Spain. Parental investment in vigilance and defence of offspring progressively decreased during the post‐fledging dependence period. The number of feeds was also slightly reduced towards the end of the period. However, this does not seem to be the main factor which leads to juvenile independence. The fact that the family rupture is sudden and that the post‐fledging dependence period tends to shorten as the season progresses suggests that juvenile and adult migratory urgency may be as important a factor as reduced parental investment in breaking the family