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

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.