Rhea is a genus of flightless bird in the family Rheidae. The genus contains two living species, the greater rhea and the lesser rhea. These birds are found in open areas of South America, such as savannas, grasslands, and forests.
The greater rhea (Rhea americana) is the largest member of the family, measuring 1.5–1.8 m (4 ft 11 in–5 ft 11 in) long and weighing 40 kg (88 lb). It is grey-brown plumage with white spots on the wings. The head is small with a long neck and bill. The legs are long and powerful, adapted for running at high speeds over long distances. This species can reach speeds of up to 60 km/h (37 mph).
The lesser rhea (Rhea pennata) is smaller than the greater rhea, measuring 1–1.4 m (3 ft 3 in–4 ft 7 in) long and weighing 15 kg (33 lb). It has similar plumage to the greater rhea but with fewer white spots on its wings. Its neck and bill are also shorter than those of the greater rhea. Like its larger relative, it is a fast runner but cannot sustain these speeds for as long periods of time.
Both species of rheas are generally shy birds but will become aggressive if they feel threatened or if their territory is invaded by another bird or animal. They will use their strong legs to kick their attacker or chase them away from their territory. If this fails to deter the intruder, they may resort to using their beak as a weapon, pecking at them until they leave.
The diet of both species consists mostly of plants although they will also eat insects, small mammals, reptiles, and amphibians if available. They spend most of their time feeding on grasses but will also eat leaves, stems, flowers, fruits, and seeds depending on what is seasonally available. Rheas swallow large quantities of food at once then store it in an enlarged pouch located just below their esophagus known as a crop where it ferments before passing into their stomach for further digestion; this allows them to extract more nutrients from plants which have low nutritional value when compared to other animals’ diets .
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