the fastest land speed of any bird.  The common ostrich is the largest living species of bird and lays the largest eggs of any living bird (extinct elephant birds of
Madagascar and the giant moa of New Zealand laid larger eggs).
The common ostrich's diet consists mainly of plant matter, though it also eats invertebrates . It lives in nomadic groups of 5 to 50 birds. When threatened, the ostrich will either hide itself by lying flat against the ground, or run away. If cornered, it can attack with a kick of its powerful legs. Mating patterns differ by geographical region, but territorial males fight for a harem of two to seven females.
The common ostrich is farmed around the world, particularly for its feathers, which are decorative and are also used as feather dusters . Its skin is used for leather products and its meat is marketed commercially, with its leanness a common marketing point. 
Common ostriches usually weigh from 63 to 145 kilograms (139–320 lb), or as much as two adult humans.  Ostriches of the East African race ( S. c. massaicus ) averaged 115 kg (254 lb) in males and 100 kg (220 lb) in females, while the nominate subspecies ( S. c. camelus) was found to average 111 kg (245 lb) in unsexed adults. Exceptional male ostriches (in the nominate subspecies) can weigh up to 156.8 kg (346 lb). At sexual maturity (two to four years), male common ostriches can be from 2.1 to 2.8 m (6 ft 11 in to 9 ft 2 in) in height, while female common ostriches range from 1.7 to 2.0 m (5 ft 7 in to 6 ft 7 in) tall.  New chicks are fawn in colour, with dark brown spots.  During the first year of life, chicks grow at about 25 cm (9.8 in) per month. At one year of age, common ostriches weigh approximately 45 kilograms (99 lb). Their lifespan is up to 40–45 years.
The feathers of adult males are mostly black, with white primaries and a white tail. However, the tail of one subspecies is buff . Females and young males are greyish-brown and white. The head and neck of both male and female ostriches is nearly bare, with a thin layer of
down .  The skin of the female's neck and thighs is pinkish gray,  while the male's is gray or pink dependent on subspecies