there are white or light-colored spots and streaks as well, mainly on the wings. The brown plumage being a sign of immaturity, it does not attract as dangerously aggressively territorial behavior as a mature black-and-white bird would. As the young birds mature, their eyes change in color from mid-grey, through light brown, to dark red. Size The black sparrowhawk is one of the world's largest Accipiters, only the Henst's, Meyer's and northern goshawk can match or exceed its size. As is common in the genus Accipiter, male black sparrowhawks are smaller than females. Typically the weights of males lie between while that of females lies in the range. The typical total length is about and wingspan about . As in most Accipiters, the tails are long (about ), as are the tarsi (about . The features of the black sparrowhawk (and Accipiters in general) are reflective of the necessity to fly through dense arboreal habitats, although this species does most of its hunting in open areas (usually from a concealed perch in a tree). Colour polymorphism The two different colour morphs (light and dark) exhibited by black sparrowhawks are inherited in a typical Mendelian manner, that suggests a one-locus, two-allele system in which the allele coding for the light morph is dominant. The frequency of the morphs varies gradually throughout the South African range of black sparrowhawks, with the frequency of dark morphs declining from over 80% in the Cape Peninsula to under 20% in the northeast. However, there are no differences of the morph distribution in relation to levels of urbanization. Dark morph black sparrowhawks might be more common on the Cape Peninsula due to pleiotropic properties of the genes that code for dark colouration, meaning that they code for an apparently unrelated trait. In the dark morph black sparrowhawk, those genes are also responsible for an improved blood parasite resistance compared to the light morph. The species breeds during the dry season in most parts of South Africa, but during the wet season on the Cape Peninsula, where blackflies and biting midges which transmit the haematozoan blood parasites (Leucocytozoon toddi and Haemoproteus nisi), may be more abundant. So, on the Cape Peninsula, black sparrowhawks gain a selective advantage from a dark colouration. When it comes to breeding on the Cape Peninsula, the morph combination of the parents also influences their productivity. Mixed‐pairs produce more offspring per year than