Havik Accipiter gentilis met een zes-legsel

In a Goshawk nest in central Friesland, occupied since at least 2010, a clutch of six eggs was found on 23 April 2017. A trail-camera was installed to check whether more than one female was involved in this breeding case (as recorded at a nearby Buzzard Buteo buteo pair in previous years). During 29 April-2 May a total of 9503 images were obtained of birds attending the nest, showing a single adult (>3-cy) female and a 3-cy male. No indication of two females attending the nest was found. Three chicks were ringed and fledged, and a single unhatched egg remained in the nest; start of laying was back-calculated – on the basis of aged nestlings (sex-specific biometry) – at 6 April. In large series of completed clutches from The Netherlands, not a single one contained 6 eggs, i.e. in Drenthe in 1984-91 (2x 1, 25x 2, 101x 3, 134x 4 and 11x 5 eggs; Bijlsma 1993), and in The Netherlands in 1996-2016 (70x 1, 437x 2, 1742x 3, 1962x 4 and 196x 5 eggs; Bijlsma in series). Curiously, in the interim of 1992-1995, three C/6 were recorded, i.e. near Nijmegen (1991; van Manen 1992) and in Drenthe (1992 and 1993; van Manen 1992, Bijlsma 1993: 131). A review of the literature showed that C/6 is rare among Goshawks (review in Van Manen 1992), as also in Schleswig-Holstein, Germany, in 1968-2017, with just one C 6 among 606 completed clutches (Looft 2017).