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Ostrich
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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.
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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 under its current binomial name. Its scientific name is derived from Latin, struthio meaning ostrich and camelus meaning camel, alluding to its dry habitat.
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.
Subspecies
Five subspecies are recognized:
- S. c. australis in Southern Africa, called the Southern Ostrich. It is found south of the Zambezi and Cunene rivers. It was once farmed for its feathers in the Little Karoo area of Cape Province.
- S. c. camelus in North Africa, sometimes called the North African Ostrich or Red-necked Ostrich. It is the most widespread subspecies, ranging from Ethiopia and Sudan in the east throughout the Sahel and the Sudan to Senegal and Mauritania in the west, and at least in earlier times north to Egypt and southern Morocco, respectively. It is the largest subspecies, at 2.74 m (9 ft) 154 kilograms (340 lb). The neck is red, the plumage of males is black and white, and the plumage of females is grey.
- S. c. massaicus in East Africa, sometimes called the Masai Ostrich. It has some small feathers on its head, and its neck and thighs are bright orange. During the mating season, the male's neck and thighs become brighter. Their range is essentially limited to southern Kenya and eastern Tanzania and Ethiopia and parts of Southern Somalia.
- S. c. syriacus in the Middle East, sometimes called the Arabian Ostrich or Middle Eastern Ostrich, was a subspecies formerly very common in the Arabian Peninsula, Syria, and Iraq; it became extinct around 1966.
- S. c. molybdophanes in southern Ethiopia, northeastern Kenya, and Somalia, is called the Somali Ostrich. The neck and thighs are grey-blue, and during the mating season, the male's neck and thighs become bright blue. 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.
Analyses indicate that the Somali Ostrich may be better considered a full species, however, the consensus among experts has not agreed upon this move. The Tree of Life project, and Avibase does recognize it as a different species, but the IOC and Birdlife does not yet. As of 2008 Birdlife.com is reviewing the proposed split. mtDNA haplotype comparisons suggest that it diverged from the other ostriches not quite 4 mya due to formation of the Great Rift Valley. Subsequently, hybridization with the subspecies that evolved southwestwards of its range, S. c. massaicus, has apparently been prevented from occurring on a significant scale by ecological separation, the Somali Ostrich preferring bushland where it browses middle-height vegetation for food while the Masai Ostrich is, like the other subspecies, a grazing bird of the open savanna and miombo habitat.
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, but as there is considerable variation of this character and there were no other differences between these birds and adjacent populations of S. c. camelus, it is no longer considered valid.
This population disappeared in the later half of the 20th century. In addition, there have been 19th century reports of the existence of small ostriches in North Africa; these have been referred to as Levaillant's Ostrich (Struthio bidactylus) but remain a hypothetical form not supported by material evidence. Given the persistence of savanna wildlife in a few mountainous regions of the Sahara (such as the Tagant Plateau and the Ennedi Plateau), it is not at all unlikely that ostriches too were able to persist in some numbers until recent times after the drying-up of the Sahara.
Evolution
The earliest fossil of ostrich-like birds is the Palaeotis living near the Asiatic steppes, from the Middle Eocene, a middle-sized flightless bird that was originally believed to be a bustard. Apart from this enigmatic bird, the fossil record of the ostriches continues with several species of the modern genus Struthio which are known from the Early Miocene onwards. While the relationship of the African species is comparatively straightforward, a large number of Asian species of ostrich have been described from very fragmentary remains, and their interrelationships and how they relate to the African ostriches is very confusing. In China, ostriches are known to have become extinct only around or even after the end of the last ice age; images of ostriches have been found there on prehistoric pottery and as petroglyphs. There are also records of ostriches being sighted out at sea in the Indian Ocean and when discovered on the island of Madagascar the sailors of the 18th century referred to them as Sea Ostriches, although this has never been confirmed.
Several of these fossil forms are ichnotaxa (that is, classified according to the organism's footprints or other trace rather than its body) and their association with those described from distinctive bones is contentious and in need of revision pending more good material.
- Struthio coppensi (Early Miocene of Elizabethfeld, Namibia)
- Struthio linxiaensis (Liushu Late Miocene of Yangwapuzijifang, China)
- Struthio orlovi (Late Miocene of Moldavia)
- Struthio karingarabensis (Late Miocene - Early Pliocene of SW and CE Africa) - oospecies(?)
- Struthio kakesiensis (Laetolil Early Pliocene of Laetoli, Tanzania) - oospecies
- Struthio wimani (Early Pliocene of China and Mongolia)
- Struthio daberasensis (Early - Middle Pliocene of Namibia) - oospecies
- Struthio brachydactylus (Pliocene of Ukraine)
- Struthio chersonensis (Pliocene of SE Europe to WC Asia) - oospecies
- Asian Ostrich, Struthio asiaticus (Early Pliocene - Late Pleistocene of Central Asia to China ?and Morocco)
- Struthio dmanisensis (Late Pliocene/Early Pleistocene of Dmanisi, Georgia)
- Struthio oldawayi (Early Pleistocene of Tanzania) - probably subspecies of S. camelus
- Struthio anderssoni - oospecies(?)
Description
Ostriches usually weigh from , although some male ostriches have been recorded with weights of up to . 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 . 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 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 in height, while female ostriches range from . During the first year of life, chicks grow about per month. At one year of age, ostriches weigh around . An ostrich can live up to 75 years.
Distribution and habitat
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 . The Arabian Ostriches in the Near and Middle East were hunted to extinction by the middle of the 20th century.
Behavior
Flocking and individual
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.
Food
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. Ostriches are known to eat almost anything (dietary indiscretion), particularly in captivity where opportunity is increased.
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 attrack hens by performing with his wings, alternating wing beats, until he attract 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 forcopulation.
Ostriches are oviparous. The females will lay their fertilized eggs in a single communal nest, a simple pit, deep and 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, long, wide, and weigh . 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.
Ostriches and people
History
Ostriches have inspired cultures and civilizations for 5,000 years in Mesopotamia and Egypt.The Kalahari still use their eggs for water jugs.
Hunting and farming
In Roman times, there was a demand for ostriches to use in venatio games or cooking. They have been hunted and farmed for their feathers, which at various times in history have been very popular for ornamentation in fashionable clothing (such as hats during the 19th century). Their skins were also valued to make goods out of leather. In the 18th century, they were almost hunted to extinction; farming for feathers began in the 19th century. The market for feathers collapsed after World War I, but commercial farming for feathers and later for skins, became widespread during the 1970s.
Ostriches are farmed in over 50 countries, including climates as cold as that of Sweden and Finland, though the majority are in Southern Africa. They will prosper in climates between 30 and −30 °C.
Since they also have the best feed to weight gain ratio of any land animal in the world (3.5:1 whereas that of cattle is 6:1), they are attractive economically to raise for meat or other uses. Although they are farmed primarily for leather and secondarily for meat, additional by-products are the eggs, offal, and feathers. Ostrich eggs can be used in a similar fashion to chicken eggs, with the average size ratio being 16 chicken eggs:1 ostrich egg.
It is claimed that ostriches produce the strongest commercially available leather. Ostrich meat tastes similar to lean beef and is low in fat and cholesterol, as well as high in calcium, protein and iron. Uncooked, it is a dark red or cherry red color, a little darker than beef.
The town of Oudtshoorn in South Africa has the world's largest population of ostriches. Farms and specialized breeding centres have been set up around the town such as the Safari Show Farm and the Highgate Ostrich Show Farm. The CP Nel Museum is a museum that specializes in the history of the ostrich.
Ostrich racing
Ostriches are large enough for a small person to ride them, typically while holding on to the wings for grip, and in some areas of northern Africa and the Arabian Peninsula ostriches are trained as racing mounts. There is little possibility of the practice becoming more widespread, due to the irascible temperament and the difficulties encountered in saddling the birds. Ostrich races in the United States have been criticized by animal rights organizations.
Ostrich feather dusters
The original South African ostrich feather dusters were invented in Johannesburg, South Africa by missionary and broom factory manager Harry S. Beckner in 1903.
Ostrich feather dusters were wound on broom handles using a foot powered kick winder and the same wire used to attach broom straw, then sorted for quality, color and length before being wound in three layers to the handle. The first layer was wound with the feathers curving inward to hide the head of the handle. The second two layers were wound curving outward to give it a full figure and its trademark flower shape.
The first ostrich feather duster company in the United States was formed in 1913 by Harry S. Beckner and his brother George Beckner in Athol, Massachusetts, and has survived till this day as the Beckner Feather Duster Company under the care of George Beckner's great granddaughter, Margret Fish Rempher. Today the largest manufacturer of ostrich feather dusters is Texas Feathers (TxF) in Arlington, Texas.
Apprentices still use the manual kick winder to learn the trade of building the hand crafted ostrich feather duster. However, to speed up the manufacturing process, factories now allow craftsmen to use electric powered winders to build the duster.
The ostrich feather is durable, soft and flexible, which accounts for the success of the ostrich feather duster over the last 100 years. Because the feather does not zipper together it is prone to developing a static charge which actually attracts and holds dust which can then be shaken out or washed off. Because of its similar makeup to human hair, care of the ostrich feather requires only an occasional shampoo and towel or air dry.
The farming of ostriches for their feathers does not harm the bird. During molting season the birds are gathered in a pen, burlap sacks are placed over their heads so they will remain calm and trained pickers pluck the loose molting feathers from the birds. The birds are then released unharmed back onto the farm.
Conservation
The ostrich has declined drastically in the last 200 years. Most surviving birds are in game parks or on farms. They are given a conservation status of Least Concern, with an occurrence range of .
Footnotes
External links
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