The rhea pennata or Darwin’s rhea is a large flightless bird, but smaller than the other species of rheas. It is common in South America, and stands at nearly one hundred meters tall. It weighs from anything between fifteen to twenty five kilos. The rhea pennata has larger wings than other ratites. This enables the Darwin’s rhea to run well and outdo potential predators. They are endowed with sharply clawed toes which form effective and lethal weapons. Their feathers are spotted white and brown, and the upper part of their tarsus is feathered. Darwin’s rhea is a name derived from Rhea, a Greek goddess, and pennata, which means ‘winged’. The name was coined by a rival of Darwin, Alcide d’Orbigny, who described the bird from a specimen from Argentina. The ‘Darwin's Rhea’ was also called ‘Rhea darwinii’ (also referred to as Rhea pennata) by another scientist in a presentation to the Zoological Society of London, in which he preceded Darwin in presenting a paper on the eggs and distribution of the two species of rheas.

The males of the rhea pennata species become very aggressive during the time of incubation. Granted, they are responsible for the incubation. The females lay the eggs close to the nest, and not inside it. Subsequently, the male then moves most of the eggs into the nest, but usually some are left outside the nest. The eggs left outside eventually rot and attract flies.

Later on, the male and the hatched chicks eat the attracted flies. The incubation period of the rhea pennata is usually between one month to about forty four days, and the number of eggs laid is between five and fifty five. The eggs are big and greenish yellow in color. When the season of mating is over and any other times outside the breeding period, the Darwin’s rheas are known to be quite sociable birds. They live in groups of from five to thirty birds of mixed sexes and different ages.

The Darwin’s Rhea is known to live in open areas of scrubs and grasslands, particularly at the Andean plateau, and also commonly found in Argentina, Chile, Bolivia and Peru. The rhea pennata is known locally by various names, depending on the location. For instance, it is called choique, suri and several other native names of the areas where it is commonly found. All the species prefer grassy, bushy or swampy habitats. However, some subspecies have been noticed to prefer high lands, albeit of less than one and a half meters.

The Darwin’s rhea can be said to be a threatened species, with the most common enemy being man who hunts it for meat and eggs, and destroys its habitation as a result of development and settlement, conversion of the habitation to agricultural land or pastures for grazing animals. The southern subspecies is relatively widespread and fairly common. However, the northern subspecies are quite threatened, and their situation very worrying, with their total combined population estimated at being in mere hundreds.