The Ostrich is a large flightless bird native to Africa and formerly the Middle East. It is the only living species of its family, Struthionidae, and its genus, Struthio. Ostriches share the order Struthioniformes with the Emu, kiwis, and other ratites. It is distinctive in its appearance, with a long neck and legs and the ability to run at speeds of about 74 km/h (46 mph), the top land speed of any bird. The Ostrich is the largest living species of bird and lays the largest egg of any bird species.
The diet of the Ostrich mainly consists of plant matter, though it eats insects. It lives in nomadic groups which contain between five and 50 birds. When threatened, the Ostrich will either hide itself by lying flat against the ground, or will run away. If cornered, it can cause injury and death with a kick from its powerful legs. Mating patterns differ by geographical region, but territorial males fight for a harem of two to seven females. The Ostrich is farmed around the world, particularly for its feathers, which are decorative and are also used for feather dusters. Its skin is used for leather and its meat marketed commercially.
Ostriches usually weigh from 93 to 130 kg (200 to 285 lb), although some male ostriches have been recorded with weights of up to 155 kg (340 lb). The feathers of adult males are mostly black, with white at the ends of the wings and in the tail. Females and young males are greyish-brown and white. The head and neck of both male and female Ostriches is nearly bare, but has a thin layer of down.
The strong legs of the Ostrich lack feathers. The bird has just two toes on each foot (most birds have four), with the nail of the larger, inner one resembling a hoof. The outer toe lacks a nail. This is an adaptation unique to Ostriches that appears to aid in running. The wings are not used for flight, but are still large, with a wingspan of around two metres (over six feet), despite the absence of long flight feathers. The wings are used in mating displays, and they can also provide shade for chicks. The feathers, which are soft and fluffy, serve as insulation, and are quite different from the flat smooth outer feathers of flying birds (the feather barbs lack the tiny hooks which lock them together in other birds). The Ostrich's sternum is flat, lacking the keel to which wing muscles attach in flying birds. The beak is flat and broad, with a rounded tip. Like all ratites, the Ostrich has no crop, and it also lacks a gallbladder.
At sexual maturity (two to four years old), male Ostriches can be between 1.8 and 2.7 m (6 to 9 ft) in height, while female Ostriches range from 1.7 to 2 m (5.5 to 6.5 ft). During the first year of life, chicks grow about 25 cm (10 in) per month. At one year of age, ostriches weigh around 45 kg (100 lb). An Ostrich can live up to 75 years.