A ratite is any of a diverse group of large, flightless birds of the order Palaeognathae. There is still some controversy regarding the systematics involved. Some sources state that Ratites are synonymous with Struthioniformes, while other sources state that Ratites are the same group, only that the order Struthioniformes contains only the Ostrich and possibly the Elephant Bird. Ratites belong to the modern bird superorder Palaeognathae which consists of ratites and tinamous (compare to Neognathae). Unlike other flightless birds, the ratites have no keel on their sternum – hence the name from the Latin ratis (for raft). Without this to anchor their wing muscles, they could not fly even if they were to develop suitable wings.
Most parts of the former Gondwana have ratites, or did have until the fairly recent past. Their closest living relatives are the tinamous of South America.
Some taxonomical systems consider the various families of ratites to be orders, but the system used here uses the order "Struthioniformes" to refer to all ratites.
The emu (pron.: //, sometimes US: /ˈiːmuː/; Dromaius novaehollandiae) is the largest bird native to Australia and the only extant member of the genus Dromaius. It is the second-largest extant bird in the world by height, after its ratite relative, the ostrich. There are three subspecies of emus in Australia. The emu is common over most of mainland Australia, although it avoids heavily populated areas, dense forest, and arid areas.
The soft-feathered, brown, flightless birds reach up to 2 metres (6.6 ft) in height. They have long thin necks and legs. Emus can travel great distances at a fast, economical trot and, if necessary, can sprint at 50 km/h (31 mph). Their long legs allow them to take strides of up to 275 centimetres (9.02 ft) They are opportunistically nomadic and may travel long distances to find food; they feed on a variety of plants and insects, but have been known to go for weeks without food. Emus ingest stones, glass shards and bits of metal to grind food in the digestive system. They drink infrequently, but take in copious fluids when the opportunity arises. Emus will sit in water and are also able to swim. They are curious birds who are known to follow and watch other animals and humans. Emus do not sleep continuously at night but in several short stints sitting down.