,
Crinifer leucogaster Most turacos are medium-sized birds – an exception being the large
great blue turaco – with long tails and short, rounded wings. They range in length from . Their flight is weak, but they are strong climbers and are able to move nimbly on branches and through vegetation. Juveniles have claws on the wings that help them climb. They have a unique foot arrangement, where the fourth toe can be brought around to the back of the foot where it almost touches the first toe, or brought around so that it is near the second and third. In spite of this flexibility the toe is actually usually held at right angles to the axis of the foot. The plumage of go-away-birds and plantain-eaters is mainly grey and white. The turacos on the other hand are brightly coloured birds, usually blue, green or purple. The green colour in turacos comes from
turacoverdin, the only true green pigment in birds known to date. Other "greens" in bird colors result from a yellow pigment such as some
carotenoid, combined with the prismatic physical structure of the feather itself which scatters the light in a particular way and giving a blue colour. Turaco wings contain the red pigment
turacin, unlike in other birds where red colour is due to carotenoids. Both pigments are derived from
porphyrins and only known from the Musophagidae into the 21st century, but especially the little-researched turacoverdin might have relatives in other birds. The incidence of turacoverdin in relation to habitat is of interest to scientists, being present in forest species but absent in savanna- and acacia-living species. ==Evolution and systematics==