Africa Wild

The ones we saw on a webcam a few days ago. I wonder how they know that they are of the same family? By instinct

Polymorphic raptors seem to prefer mates from the opposite morph. You see it often also in Wahlberg's eagles.
I think light males preferentially mate with dark females, based on the imprint of the colour morph of their mother.

There is a resaerch about the phenomon in Black Sparrowhawks

Colour morphs influence the performance and fitness of individuals through direct effects of pigment production (e.g. camouflage or thermoregulation) and indirect effects (e.g. physiological and behavioural traits). Hence, it is unlikely that different morphs are distributed randomly in the environment. Our focus species is the Black Sparrowhawk Accipiter melanoleucus, which occurs as either a dark or a light adult morph. The morph distribution of this species across South Africa follows a cline associated with rainfall seasonality and the intensity of solar radiation, with a far higher proportion of dark morphs in the Western Cape than the rest of the country. Our research has shown that provisioning rates differ depending on ambient light levels, with dark morphs providing more food to their chicks in duller light conditions than the light morph, possibly due to improved background crypsis. Thus, when the two morphs breed together in a ‘mixed’ pair, they might complement each other by expanding the conditions (daylight hour, prey or habitat types) in which parents can forage successfully. Indeed, pairs consisting of mixed-morph parents produce more offspring than parents of the same morph, and their offspring show higher survival rates. The idea that pairs consisting of the two morphs may complement each other has been termed the complementarity hypothesis.

http://www.fitzpatrick.uct.ac.za/fitz/r ... lymorphism

Black morphs are relatively common in Gabar Goshawks, and account for a significant proportion of the population in many areas. Data from southern Africa suggests dark morphs represent approximately 10% in Namibia, 15% in Zimbabwe, 11% in the South African bushveld, 7% in Kruger National Park and up to 25% in Swaziland. Interestingly, both normal grey chicks and black chicks are often raised in the same nest, suggesting that it is controlled by a recessive gene (perhaps the melanocortin 1 receptor or MC1R gene, which has been shown to code for melanin pigmentation in various vertebrates).


Polymorphism (multiple forms) is widespread in birds, occurring in at least 3.5% of all bird species. It is especially prevalent in raptors of the family Accipitridae, in which 22% of species occur in more than one morph. Just think of all the variations of e.g. Tawny Eagle, Wahlberg’s Eagle, Ayres’s Hawk Eagle, Booted Eagle, European Honey Buzzard and Common (Steppe) Buzzard. It is not common in Falconidae, but even in that family there are a few notable examples, such as the rare dark morph of Eleonora’s Falcon.


Colour polymorphism has evolved in raptors more often than in any other group of birds, suggesting that predator–prey relationships was a driving evolutionary force. Individuals displaying a new invading colour morph may enjoy an initial foraging advantage because prey have difficulties in
learning the colour of a rare morph (apostatic selection), or because morphs provide alternative foraging benefits allowing differently coloured individuals to exploit distinct food niches (disruptive selection).

Ooooh, it's complicated

Luckily there are people studying it and there is stuff for a lot of them

It is not the first time that the goshawk has done this