Struthio Camelus

The common ostrich (''Struthio camelus''), or simply ostrich, is a species of flightless bird native to certain large areas of Africa and is the largest living bird species. It is one of two extant species of ostriches, the only living members of the genus ''Struthio'' in the ratite order of birds. The other is the Somali ostrich (''Struthio molybdophanes''), which was recognized as a distinct species by BirdLife International in 2014 having been previously considered a distinctive subspecies of ostrich.

The common ostrich belongs to the order Struthioniformes. Struthioniformes previously contained all the ratites, such as the kiwis, emus, rheas, and cassowaries. However, recent genetic analysis has found that the group is not monophyletic, as it is paraphyletic with respect to the tinamous, so the ostriches are now classified as the only members of the order. Phylogenetic studies have shown that it is the sister group to all other members of Palaeognathae and thus the flighted tinamous are the sister group to the extinct moa. It is distinctive in its appearance, with a long neck and legs, and can run for a long time at a speed of with short bursts up to about , the fastest land speed of any bird. The common ostrich is the largest living species of bird and largest living dinosaur. It lays the largest eggs of any living bird (the 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 and small reptiles. 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.

Description

Common ostriches usually weigh from , or as much as one to two adult humans. The Masai ostriches of East Africa (''S. c. massaicus'') average in males and in females, while the nominate subspecies, the North African ostrich (''S. c. camelus''), was found to average in unsexed adults. Exceptional male ostriches (in the nominate subspecies) can weigh up to . At sexual maturity (two to four years), male common ostriches can be from in height, while female common ostriches range from tall. New chicks are fawn in color, with dark brown spots. During the first year of life, chicks grow at about per month. At one year of age, common ostriches weigh approximately . Their lifespan is typically 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 grayish-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.

File:Afrikanischer Strauss Portrait.jpg, Head feathers are a thin layer of down.
File:Ostrich, mouth open.jpg, Long eyelashes protect the eyes.
File:Ostrich foot.jpg, Feet are frequently missing the nail on the outer toe.
File:The Childrens Museum of Indianapolis - Ostrich skull.jpg, Skull
File:OstrichWing.jpg, Claws on the wings
File:Avestruz alta.jpg, alt=Ostrich skeleton
File:Common ostrich (Struthio camelus australis) male running composite.jpg, Male running, Namibia, alt=Male, Namibia

The long neck and legs keep their head up to above the ground, and their eyes are said to be the largest of any land vertebrate in diameter helping them to see predators at a great distance. The eyes are shaded from sunlight from above. However, the head and bill are relatively small for the birds' huge size, with the bill measuring .

Their skin varies in color depending on the subspecies, with some having light or dark gray skin and others having pinkish or even reddish skin. The strong legs of the common ostrich are unfeathered and show bare skin, with the tarsus (the lowest upright part of the leg) being covered in scales: red in the male, black in the female. The tarsus of the common ostrich is the largest of any living bird, measuring in length. The bird is didactyl, having just two toes on each foot (most birds have four), with the nail on the larger, inner toe resembling a hoof. The outer toe has no nail. The reduced number of toes is an adaptation that appears to aid in running, useful for getting away from predators. Common ostriches can run at a speed over and can cover in a single stride. The wings reach a span of about , and the wing chord measurement of is around the same size as for the largest flying birds.

The feathers lack the tiny hooks that lock together the smooth external feathers of flying birds, and so are soft and fluffy and serve as insulation. Common ostriches can tolerate a wide range of temperatures. In much of their habitat, temperatures vary as much as between night and day. Their temperature control relies in part on behavioral thermoregulation. For example, they use their wings to cover the naked skin of the upper legs and flanks to conserve heat, or leave these areas bare to release heat. The wings also function as stabilizers to give better maneuverability when running. Tests have shown that the wings are actively involved in rapid braking, turning, and zigzag maneuvers. They have 50–60 tail feathers, and their wings have 16 primary, four alular, and 20–23 secondary feathers.

The common ostrich's sternum is flat, lacking the keel to which wing muscles attach in flying birds. The beak