The growth rate (K) of young ospreys P. haliaetus L. as described by a logistic equation is 0.12; the average length of time required to grow from 10% to 90% of the asymptotic weight was 36.7 days. There was an inverse relationship between brood size and fledging weight. Young ospreys were relatively docile; cainism did not appear to exist in ospreys. During feeding, the young birds feed sequentially, and there seemed to be very little (if any) behavioral dominance manifested during feeding, which is consistent with the fact that the rank of a chick (its weight ranked relative to its siblings) often fluctuates. Unlike some other large raptors, the behavior of young ospreys did not seem to have any negative influence on the reproductive potential of the adults.