The ostrich, Struthio camelus, 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 also 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.

Taxonomy

The ostrich was originally described by Linnaeus in his 18th-century work, Systema Naturae Its scientific name is derived from Latin, struthio meaning ostrich and camelus meaning camel, alluding to its dry habitat. under its current binomial name.

The ostrich belongs to the Struthioniformes order of ratites. Other members include rheas, emu, cassowaries, and the largest bird ever, the now-extinct Elephant Bird (Aepyornis). However, the classification of the ratites as a single order has always been questioned, with the alternative classification restricting the Struthioniformes to the ostrich lineage and elevating the other groups. Presently, molecular evidence is equivocal while paleobiogeographical and paleontological considerations are slightly in favor of the multi-order arrangement

Description

Ostriches usually weigh from 63 to 130 kilograms (140–290 lb), although some male ostriches have been recorded with weights of up to 155 kilograms (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.

Their skin is variably colored dependant on the sub-species. The male tarsus has red horn plates, and the female's are black. 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). They have 50-60 tail feathers, and their wings have 16 primary, four alular and 20-23 secondary feathers. 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 They have three stomachs, and their caecae is 28 inches (71 cm). Unlike all other living birds, the ostrich secretes urine separately from feces. They also have unique pubic bones that are fused to hold their gut. The copulatory organ is retractable and 8 inches (20 cm) long. Finally, their palate is different than other ratites, in that the sphenoid and palatal bones are unconnected.

At sexual maturity (two to four years old), male ostriches can be between 1.8 and 2.8 metres (5.9 and 9.2 ft) in height, while female ostriches range from 1.7 to 2 metres (5.6 to 6.6 ft). During the first year of life, chicks grow about 25 centimetres (9.8 in) per month. At one year of age, ostriches weigh around 45 kilograms (99 lb). An ostrich can live up to 75 years.

Ostriches formerly occupied Africa north and south of the Sahara, east Africa, Africa south of the rain forest belt, and much of Asia Minor.Today, ostriches prefer open land, and are native to savannas and the Sahel of Africa, both north and south of the equatorial forest zone. In southwest Africa they inhabit the semidesert or true desert. They rarely go above 100 metres (330 ft). The Arabian Ostriches in the Near and Middle East were hunted to extinction by the middle of the 20th century.

Behavior

Social and Seasonal Behavior

Ostriches normally spend the winter months in pairs or solitary. Only 16% of ostrich sightings were of more than two birds. During breeding season and sometimes during extreme rainless periods ostriches live in nomadic groups of five to 50 birds (led by a top hen) that often travel together with other grazing animals, such as zebras or antelopes. Ostriches are diurnal, but may be active on moonlit nights. They are most active early and late in the day.
With their acute eyesight and hearing, ostriches can sense predators such as lions from far away. When being pursued by a predator, they have been known to reach speeds in excess of 70 km/h (45 mph),and can maintain a steady speed of 50 km/h (30 mph), which makes the ostrich the world's fastest two-legged animal.

When lying down and hiding from predators, the birds lay their heads and necks flat on the ground, making them appear as a mound of earth from a distance. This even works for the males, as they hold their wings and tail low so that the heat haze of the hot, dry air that often occurs in their habitat aids in making them appear as a nondescript dark lump. Contrary to popular belief, ostriches do not bury their heads in the sand. When threatened, ostriches run away, but they can cause serious injury and death with kicks from their powerful legs.Their legs can only kick forward.

Feeding

They mainly feed on seeds, shrubs, grass, and other plant matter; occasionally they also eat insects such as locusts. Lacking teeth, they swallow pebbles that help as gastroliths to grind the swallowed food in the gizzard. An adult ostrich typically carries about 1 kg of stones in its stomach. Ostriches can go without water for several days, living off the moisture in the ingested plants. However, they enjoy water and frequently take baths where it is available.dietary indiscretion), particularly in captivity where opportunity is increased. Ostriches are known to eat almost anything (

Ostriches can tolerate a wide range of temperatures. In much of its habitat, temperature differences of 40°C between night- and daytime can be encountered. Their temperature control mechanism is more complex than in other birds and mammals, utilizing the naked skin of the upper legs and flanks which can be covered by the wing feathers or bared according to whether the bird wants to retain or lose body heat.

Reproduction

Ostriches become sexually mature when they are 2 to 4 years old; females mature about six months earlier than males. The species is iteroparous, with the mating season beginning in March or April and ending sometime before September. The mating process differs in different geographical regions. Territorial males will typically use hisses and other sounds to fight for a harem of two to seven females (which are called hens). The winner of these fights will breed with all the females in an area, but will only form a pair bond with the dominant female. The female crouches on the ground and is mounted from behind by the male. The cock will attract hens by performing with his wings, alternating wing beats, until he attracts a mate. They will go to the mating area and he will maintain privacy by driving away all intruders. They graze until their behavior is synchronized, then the feeding becomes secondary and the process takes on a ritualistic appearance. The cock will then excitedly flap alternate wings again, and start poking on the ground with his bill. He will then violently flap his wings to symbolically clear out a nest in the dirt. Then, while the hen runs circle around him with lowered wings, he will wind his head in a spiral motion. She will drop to the ground and he will mount for copulation.

Ostriches are oviparous. The females will lay their fertilized eggs in a single communal nest, a simple pit, 30 to 60 centimetres (12–24 in) deep and 3 metres (9.8 ft) wide, scraped in the ground by the male. The first female to lay her eggs will be the dominant female, and when time comes to incubate, she will discard extra eggs of the weaker females, leaving behind about 20. Ostrich eggs are the largest of all eggs (and by extension, the yolk is the largest single cell, though they are actually the smallest eggs relative to the size of the bird. The nest may contain 15 to 60 eggs, which are, on average,

15 centimetres (5.9 in) long, 13 centimetres (5.1 in) wide, and weigh 1.4 kilograms (3.1 lb).

They are glossy and cream in color, with thick shells marked by small pits. The eggs are incubated by the females by day and by the male by night. This uses the coloration of the two sexes to escape detection of the nest, as the drab female blends in with the sand, while the black male is nearly undetectable in the night. The incubation period is 35 to 45 days. Typically, the male will defend the hatchlings, and teach them how and on what to feed. The survival rate is low for the eggs with an average of one per nest surviving. Predators are hyenas, jackals, and vultures.

The life span of an ostrich is from 30 to 70 years, with 50 being typical.
Ostriches reared entirely by humans may not learn to direct their courtship behaviour at other ostriches, but instead may do so at their human keepers