Common ostrich
The common ostrich, or simply ostrich, is a species of flightless bird native to certain areas of Africa. It is one of two extant species of ostriches, the only living members of the genus Struthio in the ratite group of birds. The other is the Somali ostrich, which has been recognized as a distinct species by BirdLife International since 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, a 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 bipedal animal. The common ostrich is the largest living species of bird and thus the largest living dinosaur. It lays the largest eggs of any living bird of Madagascar and the south island giant moa.
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 sold commercially, with its leanness a common marketing point.
Description
The common ostrich is the tallest and heaviest living bird. Males stand tall and weigh, whereas females are about tall and weigh. While exceptional male ostriches can weigh up to, some specimens in South Africa can only weigh between. New chicks are fawn in color, with dark brown spots. After three months they start to gain their juvenile plumage, which is steadily replaced by adult-like plumage during their second year. At four or five months old, they are already about half the size of an adult bird, and after a year they reach adult height, but not till they are 18 months old will they be fully as heavy as their parents.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 are 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.
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 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, 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 is flat and broad, with a rounded tip. Like all ratites, the ostrich has no crop, and it also lacks a gallbladder and the caecum is. Unlike all other living birds, the common ostrich secretes urine separately from feces. All other birds store the urine and feces combined in the coprodeum, but the ostrich stores the feces in the terminal rectum. They also have unique pubic bones that are fused to hold their gut. Unlike most birds, the males have a copulatory organ, which is retractable and long. Their palate differs from other ratites in that the sphenoid and palatal bones are unconnected.
Taxonomy
The common ostrich was originally described by Carl Linnaeus from Sweden in his 18th-century work, Systema Naturae under its current binomial name. Its genus is derived from the Late Latin struthio meaning "ostrich". The specific name is an allusion to "strouthokamelos" the Ancient Greek name for the ostrich, meaning camel-sparrow, the "camel" term referring to its dry habitat. Στρουθοκάμηλος is still the modern Greek name for the ostrich.The common ostrich belongs to the Infraclass Palaeognathae, commonly known as
ratites. Other members include rheas, emus, cassowaries, moa, kiwi, elephant birds, and tinamous.
Subspecies
Four subspecies are recognized:| Subspecies | Description | Image |
| North African ostrich, also known as the red-necked ostrich or Barbary ostrich | Lives in North Africa. Historically it was the most widespread subspecies, ranging from Ethiopia and Sudan in the east throughout the Sahel to Senegal and Mauritania in the west, and north to Egypt and southern Morocco, respectively. It has now disappeared from large parts of this range, and it only remains in six of the 18 countries where it originally occurred, leading some to consider it Critically Endangered. It is the largest subspecies, at in height and up to in weight. The neck is pinkish-red, the plumage of males is black and white, and the plumage of females is grey.
| |
| South African ostrich, also known as the black-necked ostrich, Cape ostrich, or southern ostrich | Found south of the Zambezi and Cunene Rivers. It is farmed for its meat, leather, and feathers in the Little Karoo area of Cape Province. | |
| Masai ostrich, also known as the pink-necked ostrich or East African ostrich | It has some small feathers on its head, and its neck and thighs are pink. During the mating season, the male's neck and thighs become brighter. Its range is essentially limited to southern Kenya and eastern Tanzania and Ethiopia and parts of southern Somalia. | |
| Arabian ostrich also known as the Syrian ostrich or Middle Eastern ostrich | Was formerly very common in the Arabian Peninsula, Syria, Iraq, and Israeli Negev; it became extinct around 1966. |
| Species | Description | Image |
| Somali ostrich, also known as the blue-necked ostrich | Found in southern Ethiopia, northeastern Kenya, and Somalia. The neck and thighs are grey-blue, and during the mating season, the male's neck and thighs become brighter and bluer. The females are more brown than those of other subspecies. It generally lives in pairs or alone, rather than in flocks. Its range overlaps with S. c. massaicus in northeastern Kenya. |
The population from Río de Oro was once separated as Struthio camelus spatzi because its eggshell pores were shaped like a teardrop and not round. As there is considerable variation of this character and there were no other differences between these birds and adjacent populations of S. c. camelus, the separation is no longer considered valid. However, a study analysing the postcranial skeleton of all living and recently extinct species and subspecies of ostriches appeared to validate S. c. spatzi based on its unique skeletal proportions. This population disappeared in the latter half of the 20th century. There were 19th-century reports of the existence of small ostriches in North Africa; these are referred to as Levaillant's ostrich but remain a hypothetical form not supported by material evidence.