It has finely blotched yellow-green plumage, a distinct facial disc of sensory, vibrissa-like feathers, a large grey beak, short legs, large feet, and wings and a tail of relatively short length. A combination of traits make it unique among its kind; it is the world's only flightless parrot, the heaviest parrot, nocturnal, herbivorous, has a low basal metabolic rate and no male parental care, and is the only parrot to have a polygynous lek breeding system. It is also possibly one of the world's longest-living birds