Kroots

The Kroot (Krootis aviana), also designated by the Imperium as Kroot Carnivore, are a xenos species of savage humanoids who are members of the T’au Empire. The Kroot evolved from avian creatures on their homeworld of Pech. Kroot are tall (a good half-metre taller than most Humans), their avian ancestry giving them a bird-like beak and long quills protruding from their heads like hair. Smaller quills, possibly the evolutionary remnants of feathers, can be found scattered over their bodies.

Source