Bal C. (1950) Over de copulaties bij Sperwers, Accipiter n. nisus (L.). ARDEA 38 (3-4): 188-190

geen Nederlandse samenvatting beschikbaar op internet Regarding coition in Sparrowhawks (Accipiter n. nisus L.). Both ornithological handbooks (Niethammer and Witherby c.s.) cite the supposition of H. Siewert (1930), that copulation takes place on the nest. I cannot agree with this for the following reasons: 1. Siewert states that he never saw copulations, but supposes that these take place on the nest, because the nest is the 'life-centre' of the birds. 2. Owen himself saw copulations. All on a branch, perhaps one on the nest. Bettmann saw a female, seated on a branch, repeatedly trodden by two different males. In literature I did not find positive observations of copulations on the nest. Holstein describes copulations of the Goshawks. These always occur on a branch in the nest-area. 3. I observed for many hours a pair of building Sparrowhawks from a hiding-tent, but never saw a single copulation at the nest. There the birds were only building. 4. The copulation I saw and the many others I heard, happened in the area, where twigs for the nest were collected, thus on a branch.