Rheas, also known as ñandúes in Spanish, or ema in Portuguese, are two species of flightless ratite birds native to South America – the greater or American rhea and the lesser or Darwin's rhea. The name was given in 1752 by Paul Mohring; his reason for choosing this name, from the Rhea of classical mythology, is not known.

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. 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 anyone — including female rheas and humans — who approach the chicks.

Rheas are omnivorous, preferring broad-leafed plants, but also eating seeds, roots, fruit, insects, and small vertebrates.

Rheas have only three toes. This is probably an adaptation to allow them to run faster than if they had four like most other birds.

Bibliography

• Folch, A. (1992). Family Rheidae (Rheas). Pp.84-89 in; del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the Birds of the World, Vol 1, Ostrich to Ducks. Lynx Edicions, Barcelona. ISBN 8487334091

External links

• Rhea videos on the Internet Bird Collection