Prooiaanvoer en jongengroei bij een één-ouder sperwernest Accipiter nisus

At a Sparrowhawk nest where the adult female had disappeared during the chick stage, the food provisioning by the male and the development of the four nestlings was measured. During the first nest visit, the chicks were between 16 and 18 days of age. As the male dropped prey items on the nest without feeding the chicks, the latter had to handle the prey by themselves. The chicks were unable to feed efficiently, resulting in a pile of prey items on the nest that was hardly eaten from. They frequently begged for food. On average, the male brought 9.8 prey items per day to the nest, which were almost exclusively caught outside the forest (90% sparrows; N=104). Two male chicks were depredated by Northern Goshawks during the nestling stage, but the other two, a male and a female, were left unharmed. In contrast to the young male, which at first hardly managed to catch on weight, the body weight of the female increased considerably. Probably, the larger female chick was better at tearing prey apart and feeding herself. By day 24, the male had reached a normal weight for its age, and the female did so by day 25 (Fig. 2). At this time, both chicks were apparently able to feed themselves properly, as could also be told from the prey remains on the nest that were stripped to the bone.