emu, (Dromaius novaehollandiae), flightless bird of Australia that is the second largest living bird: the emu is more than 1.5 metres (5 feet) tall and may weigh more than 45 kg (100 pounds). The emu is the sole living member of the family Dromaiidae (or Dromiceiidae) of the order Casuariiformes, which also includes the cassowaries.
The common emu (Dromaius novaehollandiae) is stout-bodied and long-legged, like its relative the cassowary. Both sexes are brownish, with a dark gray head and neck. Emus can dash away at nearly 50 km (30 miles) per hour; if cornered, they kick with their big three-toed feet. Emus mate for life; the male incubates 7 to 10 dark green eggs, 13 cm (5 inches) long, in a ground nest for about 60 days. The striped young soon run with the adults. In small flocks, emus forage for fruits and insects but may also damage crops. The peculiar structure of the trachea of the emu is correlated with the loud booming note of the bird during the breeding season. Three subspecies are recognized, inhabiting northern, southeastern, and southwestern Australia; a fourth, now extinct, lived on Tasmania.
The common emu is the only survivor of several forms exterminated by European settlers. The International Union for the Conservation of Nature and Natural Resources (IUCN) lists the common emu as a species of least concern. Ecological studies estimate that there are more than 630,000 adult emus and note that emu populations are likely stable. The King Island emu (D. minor), a species found only on King Island in the Bass Strait, was last seen in the wild in 1802, and the last captive specimens died in 1822. The Kangaroo Island emu (D. baudinianus), found only on Kangaroo Island in South Australia, was likely hunted to extinction prior to 1827.