The vangas are an example of
adaptive radiation, having evolved from a single founding population into a variety of forms adapted to various
niches occupied by other bird families in other parts of the world. They differ in size, colour and bill shape but are similar in
skull shape and
bony palate structure. They are small to medium-sized birds, varying from 12 to 32 cm in length. Many have strong, hooked bills similar to those of shrikes. The
helmet vanga has a particularly large bill with a
casque on top. Other species, such as the
newtonias, have a small, thin bill. The
sickle-billed vanga is notable for its long, curved bill used to probe into holes and cracks. Most vangas are largely black, brown or grey above and white below. Exceptions include the blue and white
blue vanga and the blue-grey
nuthatch vanga. The helmet vanga is mostly black with a rufous back. Male
Bernier's vangas are entirely black while the females are brown. It is one of several species with distinct male and female plumage while in other species the sexes are identical. Most vangas have whistling calls. == Distribution and habitat ==