The flightless greater rhea (Rhea americana) is the largest bird in the South America. Although it is unable to fly, rhea can run very fast and reach up to 40 miles per hour. Wings provide stability during running. Rhea is a silent animal most of the time, but during the mating season males produce sounds that are similar to the roars of mammals. Unlike other animals, males are fully responsible for building of the nest and care of the eggs and chicks after hatching. There are two species of rhea: Greater or American Rhea and Darwin's Rhea. They differ in size and in type of habitat they inhabit. Rhea can be found in open grasslands, pampas and woodlands of Argentina, Uruguay, Bolivia, Paraguay, Chile, Peru and Brazil. Rhea is also kept on farms because of its meat, eggs and skin.