Rheas | Rheiformes

Nandoeachtigen | Reiformes | Rheas

The rheas form an order with a single family and belong to the palaeognaths, the ancient branch that also includes the ostriches, emus, cassowaries, kiwis and the tinamous. The large, flightless members of this branch are together called ratites, but genetic studies indicate that they do not form a separate group: the flying tinamous sit within it, and flight was probably lost independently more than once. Characteristic of the order are the flat breastbone without a keel, the simple, loose plumage without cohesive vanes and the palate, which is built differently from that of other birds. Rheas live only in South America, in open landscapes from the high Andean plateau to lowland savannas and the pampas. Here too the male incubates and alone cares for the young, while several females lay in a single nest. In this guide the order is represented by two species of the rhea family (Rheidae): Lesser Rhea on the puna and Greater Rhea in the lowlands of eastern Bolivia.

Families in this order

Rheas | Rheidae2 speciesThe family has two species in a single genus, and both occur in this guide, in very different landscapes. Lesser Rhea is found here in the form of the Puna Rhea on the high plateau of southern Peru and western Bolivia, in open grassland and scrub of the puna, often above 3,500 metres. Greater Rhea belongs to the lowlands and in this guide occurs in the savannas and dry Chaco forest of eastern Bolivia. Rheas are the largest birds of South America: flightless running birds with a long neck, long, powerful legs with three toes and soft, loose plumage in grey and brown. The wings are fairly large and are spread while running to steer and to change direction abruptly. They feed mainly on leaves, seeds and fruit, supplemented by insects and small vertebrates. Outside the breeding season they live in groups, often together with grazing livestock or wild camelids. In the breeding season the male gathers several females, which lay their eggs together in a single scrape on the ground; the male incubates them alone and fiercely defends the young. Hunting and egg collecting have greatly reduced their numbers in many places.