Editing Common ostrich (section)

==Description==
The common ostrich is the tallest and heaviest living bird. Males stand {{cvt|2.1|to|2.75|m}} tall and weigh {{cvt|100|to|130|kg}}, whereas females are about {{cvt|1.75|to|1.9|m}} tall and weigh {{cvt|90|to|120|kg}}.<ref name =world>Del Hoyo, Josep, et al. Handbook of the birds of the world. Vol. 1. No. 8. Barcelona: Lynx edicions, 1992.</ref> While exceptional male ostriches (in the nominate subspecies) can weigh up to {{cvt|156.8|kg}}, some specimens in South Africa can only weigh between {{cvt|59.5|to|81.3|kg}}.<ref>Urban, Emil K. "Roberts Birds of Southern Africa." (2007): 1104-1106.</ref> New chicks are [[wiktionary:fawn|fawn]] in color, with dark brown spots.<ref name = Perrins2/> 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.<ref name =world/>

The feathers of adult males are mostly black, with white [[flight feathers#Primaries|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 feather|down]].<ref name="Gilman 1903"/><ref name=Perrins2/> The skin of the female's neck and thighs is pinkish gray, while the male's is gray or pink dependent on subspecies.<ref name=Perrins2/>

<gallery mode="packed">
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]]
</gallery>

The long neck and legs keep their head up to {{cvt|2.8|m}} above the ground, and their eyes are said to be the largest of any land vertebrate {{endash}} {{cvt|50|mm}} in diameter<ref name=Brown/> {{endash}} helping them to see predators at a great distance. The eyes are shaded from sunlight from above.<ref name=Martin2000/><ref name=Martin2001/> However, the head and [[Beak|bill]] are relatively small for the birds' huge size, with the bill measuring {{cvt|12|to|14.3|cm}}.<ref name="Davies"/>

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 (skeleton)|tarsus]] (the lowest upright part of the leg) being covered in scales: red in the male, black in the female. The [[Tarsus (skeleton)|tarsus]] of the common ostrich is the largest of any living bird, measuring {{cvt|39|to|53|cm}} in length.<ref name="Davies"/> The bird is [[didactyl]], having just two toes on each [[Bird feet and legs|foot]] (most birds have four), with the [[nail (anatomy)|nail]] on the larger, inner toe resembling a [[hoof]]. The outer toe has no nail.<ref>{{cite web|url=http://www.thewonderofbirds.com/biology/claws.htm|publisher=TheWonderofBirds.com|title=Bird claws or nails|access-date=22 January 2015}}</ref> 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 {{cvt|70|km/h}} and can cover {{cvt|3|to|5|m}} in a single stride.<ref>[http://www.sandiegozoo.org/animalbytes/t-ostrich.html San Diego Zoo's Animal Bytes: Ostrich]. Sandiegozoo.org. Retrieved on 21 August 2012.</ref> The wings reach a span of about {{cvt|2|m}}, and the [[Wing chord (biology)|wing chord]] measurement of {{cvt|90|cm}} is around the same size as for the largest flying birds.<ref name="Davies"/>

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 {{cvt|40|C-change}} 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.<ref>{{cite web|url=http://www.livescience.com/6657-ostrich-wings-explain-mystery-flightless-dinosaurs.html|title=Ostrich Wings Explain Mystery of Flightless Dinosaurs|website=[[Live Science]]|date=30 June 2010}}</ref> They have 50–60 tail feathers, and their wings have 16 primary, four [[alular]], and 20–23 secondary feathers.<ref name="Davies"/>

The common ostrich's [[sternum]] is flat, lacking the [[Keel (bird)|keel]] to which wing muscles attach in flying birds.<ref name="Nell 2003"/> The [[beak]] is flat and broad, with a rounded tip.<ref name="Gilman 1903"/> Like all [[ratites]], the ostrich has no [[Crop (anatomy)|crop]],<ref name=Brand2006/> and it also lacks a [[gallbladder]]<ref name=Marshall/> and the [[caecum]] is {{cvt|71|cm}}. Unlike all other living birds, the common ostrich secretes urine separately from feces.<ref name=coprodeum/> All other birds store the urine and feces combined in the [[coprodeum]], but the ostrich stores the feces in the terminal rectum.<ref name=coprodeum/> They also have unique [[pubic bones]] that are fused to hold their gut. Unlike most birds, the males have a [[Intromittent organ#Birds|copulatory organ]], which is retractable and {{cvt|20|cm}} long. Their [[palate]] differs from other ratites in that the [[Sphenoid bone|sphenoid]] and [[palatal]] bones are unconnected.<ref name="Davies"/>