The rheas are species of flightless ratite birds in the genus Rhea, native to South America. There are two extant species: the Greater or American Rhea and the Lesser or Darwin's Rhea. The genus name was given in 1752 by Paul Mohring and adopted as the English common name. Mohring's reason for choosing this name, from the Rhea of classical mythology, is not known.
Description and biology
Rheas are large, flightless birds with grey-brown plumage, long legs and long necks. These birds stand to about the size of 5 feet 5 inches (1.68 m). Their wings are comparatively large for a flightless bird and are spread while running, to act like sails. Unlike most birds, rheas have only three toes which is probably an adaptation to allow faster running. They are omnivorous, preferring broad-leafed plants, but also eating seeds, roots, fruit, insects, and small vertebrates.
The recognised subspecies are:
- Greater Rhea Rhea americana
- R. a. americana, found in campos of north and east Brazil
- R. a. intermedia, southeast Brazil (Rio Grande do Sul) and Uruguay
- R. a. nobilis, east Paraguay
- R. a. araneipes, Paraguay to Bolivia and Brazilian Mato Grosso>
- R. a. albescens, plains of Argentina south to Rio Negro
- Lesser Rhea Rhea pennata
- R. p. garleppi
- R. p. tarapacensis
- R. p. pennata
Rheas are polygamous, with males courting between two to twelve females. After mating, the male builds a nest, in which each female lays her eggs in turn. The nest consists of a simple scrape in the ground, lined with grass and leaves. The male incubates from ten to sixty eggs; the chicks hatch within 36 hours of each other. The females, meanwhile, may move on and mate with other males. While caring for the young, the males will charge at any perceived threat that approach the chicks including female rheas and humans. The young reach full adult size in about six months, but do not breed until they reach two years of age.