Rhea (bird) many people. The gaucho people traditionally hunt rheas on horseback, throwing "bolas" or "boleadoras" — a throwing device consisting of three balls joined by rope — at their legs, which immobilises the bird. The rhea is pictured on Argentina's 1 Centavo coin minted in 1987, and on the Uruguayan 5 peso coin. Rhea (bird) The rheas () are large ratites (flightless birds without a keel on their sternum bone) in the order Rheiformes, native to South America, distantly related to the ostrich and emu. Most taxonomic authorities recognize two extant species: the greater or American rhea ("Rhea americana") and the
Flightless bird oceanic islands. Incongruences between ratite phylogeny and Gondwana geological history indicate the presence of ratites in their current locations is the result of a secondary invasion by flying birds. It remains possible that the most recent common ancestor of ratites was flightless and the tinamou regained the ability to fly However, it is believed that the loss of flight is an easier transition for birds rather than the loss and regain of flight, which has never been documented in avian history. Moreover, tinamou nesting within flightless ratites indicates ancestral ratites were volant and multiple losses of flight occurred independently throughout