Rheas are similar in appearance to ostriches, but they are smaller and live in South America instead of Africa. The two species of rheas, often called South American ostriches, vary in size and location. The common rhea (Rhea americana) of Argentina and Brazil stands 5 ft (1.5 m) tall, several feet shorter than an ostrich, but it is still the largest North or South American bird. Darwin's rhea (Pterocnemia pennata) of southern Peru to the Patagonian region of Argentina is considerably smaller and has white tips on its brown plumage. Rheas live on open grassy plains in most of South America except the Andes Mountains and the northeastern region along the Atlantic. They can usually be found in flocks of about 50 birds, often in the vicinity of cattle herds.
Rhea males attract females by swinging their heads from side to side and making a loud, roaring sound. The females are mute. Unlike ostriches, a rhea male lines the nest with leaves and assumes total responsibility for incubating the eggs. The male incubates the eggs of five or six females for about five weeks, and then takes care of the young. The eggs are dark green, almost black, in color.