There are two species of birds in this family. They are found on grasslands in South America.

Rheas eat leaves, roots, seeds, grass, insects, and small mammals, reptiles, and amphibians. Rheas have long necks, long, powerful legs, and shaggy gray feathers.

The male rhea mates with as many as 8 females. Each female lays as many as 20 eggs in a single nest. The male incubates all the eggs for 35 to 40 days.

Male rheas have been known to incubate as many as 60 eggs at a time. The male cares for the chicks and charges after any threat that comes too close to his chicks.