The male has a red "cap" at the top of his head, which is reduced to a red nape in the female. A tireless drummer, this bird hollows out holes in the trees in which to raise his young, but also to dislodge grubs and insects hidden in the wood. The beak grows continually to compensate for the wear it is subjected to. The bone structure of the head is reinforced. The skull and beak are separated by shock absorbing cartilage.