Rheas: Order Rheiformes

The Rheiformes, contain two species of Neotropical flightless birds in two genera: the Greater Rhea, Rhea americana, and the smaller Lesser Rhea, Rhea pennata.

The rheas roam the South American grasslands, in a similar way that Ostriches roam the African grasslands. Their sexes are not dimorphic, meaning it is difficult to tell whether an adult rhea is male or female. Like other rattites, rheas are tall. The common rhea can reach 5 feet. When the rheas run, they do use their wings, but not to fly. As they turn they will use them as a sort of 'sail'. Like other large, fast land birds, their toes have been reduced to three, which helps in speed. They are gregarious birds, normally found in flocks. During the breeding season they will breed in harems.

Classification

• Greater Rhea (also known as the Common or American Rhea): Rhea americana
• Lesser Rhea (also known as Darwin's Rhea): Rhea pennata