As promised, Flightless Friday returns! After covering penguins, we move on to ratites, which are a varied group of large flightless birds that were all previously assigned to the order Struthioniformes, to which ostriches still belong but other species have been more accurately classified.

Darwin’s Rhea (Rhea pennata), also called the Lesser Rhea, can be found in the Patagonian and Altiplano regions of South America. It is the smaller of the two extant species of rhea, and prefers to live in grasslands, sub-steppes, pumice flats. During breeding season, however, it nests in areas that are close to bodies of water. In Argentina, it’s known as ñandú del norte or ñandú petiso, which is derived from the Guarani term “big spider.” The spider reference might be a reference to the way Darwin’s Rhea waves its wings when it runs. Other local names include choique and suri.

Darwin’s Rhea has a large body, thin legs with strong muscles, and a long slender neck. Its plumage is usually brown and white, and the upper parts of its legs are feathered. The lower legs have 18 plates protecting them in the front. They stand about 39 inches (100 cm) tall and are just about as long. They weigh approximately 63 pounds (29 kg) and are good runners. Darwin’s Rhea can reach speeds of up to 37 miles per hour (60 km/h), which allows them to outrun their natural predators.

The majority of the Darwin Rhea’s diet consists of vegetation, like seeds and grasses, but they will also eat insects and even small lizards and mammals when they can get them. They are often observed to graze alongside guanacos, llamas, vicuñas or even domestic livestock. There are currently three recognized subspecies of Darwin’s Rhea:

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  • Rhea pennata pennata (Patagonia [Argentina and Chile])
  • Rhea pennata garleppi (southern Peru, Bolivia and northern Argentina)
  • Rhea pennata tarapacensis (northern Chile)

The breeding season of Darwin’s Rhea occurs in July and August, during which the females form smaller groups of their own, within the mixed groups of about 30. The males will then try to entice the groups of females to stay in their territory, which they defend against rivals. The male will mate with several females, who then lay their eggs in a communal nest that the male constructs by digging a hole and lining it with vegetation. Females can lay multiple clutches per season, and mate with multiple males. Each male is responsible for the incubation of his eggs, sitting on and guarding the eggs for 40 days. After the chicks hatch, the male leads them away after a few days and raises them until they are a few months old. They will reach almost their adult size by 8 or 9 months.

Darwin’s Rhea is considered to be near threatened by the IUCN, with two of the subspecies (R. p. garleppi and R. p. tarapacensis) suffering significant population declines - combined, they number only a few hundred birds. Darwin’s Rhea are hunted for meat and skin, and eggs and chicks are taken from the wild for domestication. All three subspecies are threatened by habitat loss, as their grasslands and sub-steppes are converted to farmland or over-grazed and desertified.

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Source for all images used in this post.