Rheas are large, flightless birds with grey-brown plumage, long legs and long necks, similar to an ostrich. Large males of R. americana can reach 67 in tall at the head, 39 in at the back and can weigh up to 88 lbs.
Their wings are large for a flightless bird at 8.2 ft and are spread while running, to act like sails.
Unlike most birds, rheas have only three toes. Their tarsus has 18 to 22 horizontal plates on the front of it. Rheas are from South America only and are limited within the continent to Argentina, Bolivia, Brazil, Chile, Paraguay, Peru, and Uruguay. They are grassland birds and both species prefer open land.
They prefer to breed near water and prefer lowlands, seldom going above 4,900 ft. Both the Lesser Rhea and the Greater Rhea are seeing shrinking wild numbers and shrinking habitat. Both are considered near threatened by the IUCN and have been for the last 15 years.
The IUCN also states that they are both approaching vulnerable status.