The female of the species is a ground-living bird, resembling a typical-looking tinamou, very much larger than the male whom she carries around on her back. The male's wings and digestive system are degenerate and he is entirely parasitic on the female, sucking her blood through his needle-shaped beak. The male's only biological function is to provide sperm during mating. This relationship arises from the species' low population density, which makes it an advantage for each female to have a mate constantly available rather than to search for one each breeding season.