Standing up to two metres tall, adult male emus are Australia's largest birds. In size, they are second only to ostriches in the world. Their powerful legs give them great speed, some running up to 50 kilometres per hour. At full pace, an emu's stride can measure up to three metres. The emu belongs to a group of flightless running birds with flat breastbones known as ratites .
Ratites are the oldest of modern bird families.
They include kiwis, ostriches and cassowaries. The emu's feathers are very primitive and look like a form of coarse hair. The special nature of these feathers enables emus to endure extreme changes in weather. The emu's tracheal pouch, which is part of its windpipe, is used for communication. It is over 30 centimetres long and very thin-walled, and it allows the bird to produce deep guttural grunts.