parrots, and red-bellied parrots are dimorphic, the other species of Poicephalus parrots cannot be distinguished by the colours of their plumage. The difference is especially clear in red-bellied parrots, where males have red or bright orange plumage on breast, belly and below their wings while the feathers of females are all grey-brown in these areas. The smallest species in the genus is the Meyer's parrot, with adults reaching a body-length of only 22 centimeters (≈ 8,66 in.) and weighing approximately 120 g (≈ 4,23 oz). The largest species, the Cape parrot, by contrast, is usually almost as large as an African grey parrot, adult males reaching a size of 32 centimeters (≈ 12,6 in.) and a weight of about 400 g (≈ 14,1 oz). Many Poicephalus parrots have bulky heads and powerful beaks, the colour of which varying with the species. While brown-headed parrots and Niam-Niam parrots have a grey upper mandible and an off-white lower one, other species have a homogeneously grey-coloured beak or a horn-coloured one with a darker tip. The Cape parrot stands out with a particularly sturdy beak in relation to its overall size which it needs to obtain its main food source, the hard-shelled fruit of Podocarpus trees. British parrot specialist Rosemary Low has pointed out that, among the genus, only the Cape parrot is able to crack open walnuts with its beak. Except for macaws, this is a rare ability among parrots in general. Distribution All ten species of Poicephalus parrots live in Africa, south of the Sahara. Their natural habitat ranges from the coastal regions of the Red Sea and the Gulf of Aden in the north to the Drakensberg in South Africa and the northern edge of the Kalahari Desert and the Namib in the south. Thus Poicephalus parrots can be found in any tropical and subtropical habitat across Africa, except the high-altitude mountains, although they also live in the subtropical Afromontane regions and a geographical region where Kalahari desert and the South African Highveld merge. The Sahel and the two other deserts within their habitat (Namib and Kalahari Desert) are natural distribution boundaries because they are no appropriate biotopes for parrots. To the southeast, increasing deforestation limits their range. So much so that the Cape parrot populations, already considered one of the most threatened large parrot species of Africa, have become disjunct in an area reaching from the Eastern Cape Province