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Lo struzzo (Struthio camelus, Linnaeus 1758) è una specie di uccello dell'ordine degli Struthioniformes che, anche per via della sua incapacità di volare, risulta essere il più grande tra i pennuti viventi.
È distribuito naturalmente in Africa in particolare nell'area sub-sahariana, Sahel, Corno d'Africa, Somalia, Kenya, Tanzania ed Africa meridionale, ed è stato introdotto in Australia dall'uomo.
La specie è suddivisa in quattro sottospecie:
* struzzo africano subsahariano o del nord (Struthio camelus camelus)
* struzzo somalo (Struthio camelus molybdophanes)
* struzzo masai (Struthio camelus massaicus)
* struzzo australe o sudafricano (Struthio camelus australis).
FONTE IMMAGINE: http://commons.wikimedia.org/wiki/File:Afrikanischer_Strauss_Portrait.jpg
Author: Thomas Pries
FONTE IMMAGINE: http://commons.wikimedia.org/wiki/File:Struthio_camelus_-_Strausskueken.jpg
Il nome scientifico dello struzzo (Struthio camelus) contiene un accostamento che era già stato fatto dagli antichi, quello fra l'uccello ed il cammello, nel quale si specchia una delle caratteristiche fondamentali della specie: anche lo struzzo, infatti, è un vero e proprio prodotto del deserto e delle steppe, e possiede una struttura e delle proprietà esattamente rispondenti alle esigenze poste dall'ambiente entro il quale si trova a vivere.
Ha un corpo molto robusto, il collo lungo e in gran parte nudo, la testa piccola e piatta, il becco dritto, ottuso, poco arrotondato nella parte anteriore e piatto in punta; le mascelle sono pieghevoli, e si spalancano in uno squarcio che giunge fin sotto l'occhio, ed all'incirca alla metà di quella superiore si aprono le narici, divaricate e piuttosto lunghe. Gli occhi sono lunghi e lucenti, con la palpebra superiore provvista di ciglia, le orecchie sono nude, aperte, rivestite internamente di produzioni filiformi, le zampe alte e robuste, del tutto nude, a parte alcune setole che spuntano sulle cosce. I tarsi sono coperti da larghe squame, e le zampe hanno due dita, l'interno fornito di un'unghia grande, larga e ottusa.
Ancorché grandi, le ali sono del tutto inutili per il volo, rivestite, invece che delle normali remiganti, di piume lunghe, flosce e pendenti che si ritrovano identiche nell'abbondante coda, e il resto del corpo è coperto da un piumaggio floscio ed arricciato, che nel mezzo del petto lascia scoperta una callosità di consistenza cornea.
Di grandissima mole, lo struzzo ha un'altezza non inferiore ai due metri e mezzo, ed una lunghezza, dalla punta del becco alla fine della coda, di almeno un metro e ottanta: il suo peso raggiunge i 150 kg.
Quanto al colore, in generale esso si differenzia tra i due sessi. Il maschio ha tutte le piume del tronco di color nero-carbone, quelle della coda e dell'ala bianche, il collo rosso-vivo e le cosce carnicine; le femmine sono grigio-brune e bianco-sporche sulle ali e sulla coda, e ripetono la colorazione dei compagni negli occhi bruni e nel becco giallo-corneo.
Corre molto rapidamente e può raggiungere una velocità massima di circa 70 km/h, il che lo rende il più veloce uccello corridore.
Durante il periodo della riproduzione i branchi di struzzi si sciolgono in famiglie composte di un maschio e di due-quattro femmine, che occupano una zona di territorio piuttosto ampia e non se ne allontanano: condizione necessaria perché esse si stabiliscano entro un'area determinata, più che l'abbondanza di cibo, che riescono sempre a rintracciare, è la vicinanza dell'acqua, elemento essenziale per la loro sussistenza. Se le variazioni climatiche non influiscono troppo sul mondo vegetale, lo struzzo non sente la necessità di compiere grossi spostamenti, e si mantiene tranquillo per tutto l'anno entro gli stessi confini.
Tra i suoi sensi, il più sviluppato è certamente quello della vista; udito ed odorato sono buoni, ottusi invece il tatto ed il gusto. Qualche discussione si accese in passato tra i naturalisti a proposito delle sue facoltà intellettive, perché a qualcuno pareva di non poter condividere un'altra opinione della Bibbia, secondo la quale Dio tolse allo struzzo la sapienza e non gli diede nessuna intelligenza, e di dover viceversa riconoscere all'uccello un buon grado di prudenza e di circospezione. Ogni divergenza si è però appianata nell'ammissione della estrema ristrettezza delle sue facoltà: è vero che lo struzzo è un uccello circospetto e prudente, ma queste caratteristiche dell'indole non hanno il soccorso di nessuna concreta capacità di valutazione. Qualsiasi fatto nuovo, qualsiasi presenza estranea hanno per effetto di atterrirlo nella stessa misura, indipendentemente dal reale grado di pericolosità che comportano; lo struzzo non sa valutare né distinguere le minacce serie dagli avvenimenti strani ma del tutto inoffensivi, e si lascia atterrire dagli animali più innocui.
[modifica] Leggenda della testa sotto la sabbia
Ad un osservatore inesperto può sembrare che lo struzzo metta la testa sotto la sabbia, ma in realtà si china con il collo disteso e con il corpo appoggiato a terra cercando di imitare un cespuglio o una grossa roccia, e se il predatore si avvicina troppo, scappa a grandi falcate che raggiungono i 70 km/h.FONTE:
From Wikipedia, the free encyclopedia
The Ostrich, (Struthio camelus), is a large flightless bird native to Africa. It is the only living species of its family, Struthionidae and its genus, Struthio. Ostriches share the order Struthioniformes with the kiwis, emus, and other ratites. It is distinctive in its appearance, with a long neck and legs and the ability to run at maximum speeds of about 70 kilometres per hour (43 mph), the top land speed of any bird. The Ostrich is the largest living species of bird and lays the largest egg of any living bird (extinct elephant birds of Madagascar and the giant moa of New Zealand did lay larger eggs).
The diet of the Ostrich mainly consists of plant matter, though it also eats invertebrates. It lives in nomadic groups which contain between five and fifty birds. When threatened, the Ostrich will either hide itself by lying flat against the ground, or will run away. If cornered, it can attack 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. These fights usually last just minutes, but they can easily cause death through slamming their heads into opponents.
The 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 marketed commercially.
Ostriches usually weigh from 63 to 130 kilograms (140–290 lb), with exceptional male Ostriches weighing up to 155 kilograms (340 lb). 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 females neck and thighs is pinkish gray, while the male's is blue-gray, gray or pink dependent on subspecies.
The long neck and legs keep their head 1.8 to 2.75 metres (6 to 9 ft) above the ground, and their eyes are said[by whom?] to be the largest of any land vertebrate – 50 millimetres (2.0 in) in diameter; they can therefore perceive predators at a great distance. The eyes are shaded from sun light falling from above.
Their skin varies in colour depending on the sub-species. The strong legs of the Ostrich are unfeathered and show bare skin, with the tarsometatarsus (the lowest upright part of the leg) being covered in scales – red in the male, black in the female. The bird has 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. Ostriches can run at over 70 kilometres per hour (43 mph) for up to 30 minutes. The wings reach a span of about 2 metres (6 ft 7 in) and are used in mating displays and to shade chicks. 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. 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 the caecum is 71 centimetres (28 in) long. Unlike all other living birds, the Ostrich secretes urine separately from faeces. Contrary to all other birds who store the urine and faeces combined in the coprodeum, they store the faeces 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 8 inches (20 cm) long. Their palate differs from other ratites in that the sphenoid and palatal bones are unconnected.
At sexual maturity (two to four years), male Ostriches can be from 1.8 to 2.8 metres (5 ft 11 in to 9 ft 2 in) in height, while female Ostriches range from 1.7 to 2 metres (5 ft 7 in to 6 ft 7 in). During the first year of life, chicks grow about 25 centimetres (10 in) per month. At one year of age, Ostriches weigh around 45 kilograms (100 lb). Their lifespan is up to 40 or 45 years.
A female ostrich can determine her own eggs amongst others in a communal nest.
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:Ostrich_Foot.jpg
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:Ostriches_cape_point_cropped.jpg
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 ratite order Struthioniformes. Other members include rheas, emus, cassowaries, moa, kiwi 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.
Five subspecies are recognized:
* S. c. australis, Southern Ostrich, southern Africa. 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, North African Ostrich or Red-necked Ostrich, 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 6 of the 18 countries where it originally occurred, leading some to consider it Critically Endangered. It is the largest subspecies, at 2.74 metres (9.0 ft) in height and up to 154 kilograms (340 lb) in weight. The neck is pinkish-red, the plumage of males is black and white, and the plumage of females is grey.
* S. c. massaicus, Masai Ostrich, East Africa. 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. Their range is essentially limited to southern Kenya and eastern Tanzania and Ethiopia and parts of Southern Somalia.
* S. c. syriacus, Arabian Ostrich or Middle Eastern Ostrich, Middle East. Was formerly very common in the Arabian Peninsula, Syria, and Iraq; it became extinct around 1966.
* S. c. molybdophanes, Somali Ostrich, 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.
Some analyses indicate that the Somali Ostrich may be better considered a full species, but there is no consensus among experts about this. The Tree of Life Project and IOC recognize it as a different species, but The Clements Checklist of Birds of the World, Howard and Moore Complete Checklist of the Birds of the World and BirdLife International do not. As of 2010 BirdLife International is reviewing the proposed split. Mitochondrial DNA haplotype comparisons suggest that it diverged from the other Ostriches not quite four mya due to formation of the Great Rift Valley. 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. However, 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. 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 (Struthio bidactylus) but remain a hypothetical form not supported by material evidence.
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 fragmentary remains, and their interrelationships and how they relate to the African Ostriches is 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 petroglyphs. There are also records of Ostriches being sighted on islands of 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[verification needed].
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)
* Giant Ostrich, Struthio dmanisensis (Late Pliocene/Early Pleistocene of Dmanisi, Georgia)
* Struthio oldawayi (Early Pleistocene of Tanzania) - probably subspecies of S. camelus
* Struthio anderssoni - oospecies (?)
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 the savannas and 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.
Social and seasonal behaviour
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:FlappingOstriches.jpg
Ostriches normally spend the winter months in pairs or alone. Only 16 percent 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. The male ostrich territory is between 2 and 20 km2 (0.77 and 7.7 sq mi).
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 kilometres per hour (43 mph), and can maintain a steady speed of 50 kilometres per hour (31 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.
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. Contrary to popular belief, Ostriches do not bury their heads in sand. This myth likely began with Pliny the Elder (AD 23-79), who wrote that Ostriches "imagine, when they have thrust their head and neck into a bush, that the whole of their body is concealed."
Ostriches and humans
Hunter-gatherers in the Kalahari use ostrich eggshells as water containers in which they puncture a hole to enable them to be used as canteens. The presence of such eggshells with engraved hatched symbols dating from the Howiesons Poort period of the Middle Stone Age at Diepkloof Rock Shelter in South Africa suggests ostriches were an important part of human life as early as 60,000 BP.
Ostriches have inspired cultures and civilizations for 5,000 years in Mesopotamia and Egypt. A statue of Arsinoe II of Egypt riding an Ostrich was found in a tomb in Egypt. The Kalahari bushmen still use their eggs as 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 have been popular for ornamentation in fashionable clothing (such as hats during the 19th century). Their skins are valued for their 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 so adaptable that they can be farmed in climates ranging from South Africa to Alaska.
It is claimed that Ostriches produce the strongest commercial 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 dark red or cherry red, a little darker than beef.
A Jacksonville, Florida, man with an Ostrich-drawn cart, circa 1911
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:OstrichCartJacksonville1.jpg
In some countries, people race each other on the back of Ostriches. The practice is common in Africa and is relatively unusual elsewhere. The Ostriches are ridden in the same way as horses with special saddles, reins, and bits. However, they are harder to manage than horses.
The racing is also a part of modern South African culture. Within the United States, a tourist attraction in Jacksonville, Florida called 'The Ostrich Farm' opened up in 1892; it and its races became one of the most famous early attractions in the history of Florida.
In the United States, Chandler, Arizona hosts the annual 'Ostrich Festival' which features ostrich races. Racing has also occurred at many other locations such as Virginia City in Nevada, Canterbury Park in Minnesota, Prairie Meadows in Iowa, and Ellis Park in Kentucky.
The wild Ostrich population has declined drastically in the last 200 years, with most surviving birds in reserves or on farms. However, its range remains very large, leading the IUCN and BirdLife International to treat it as a species of Least Concern. Of its 5 subspecies, the Middle Eastern Ostrich (S. c. syriacus) became extinct around 1966, and the North African Ostrich (S. c. camelus) has declined to the point where it now is included on CITES Appendix I and some treat it as Critically Endangered.
FONTE IMMAGINE: http://en.wikipedia.org/wiki/File:Yaen002.jpg