Ratite is the common term for a variety of flightless birds characterized by a flat, raftlike sternum rather than the keeled sternum, designed to support flight muscles, typical of most birds. Once used more technically, ratite, or Ratitae, is today but a loose covering term for a number of bird orders whose members possess such a breast shape. It is generally recognized, however, that the common morphology shared by these assorted birds is the product of a shared adaptation to ground living rather than of a common evolutionary descent. While ratites were formerly thought to be ancestral to the carinates, or flying birds, they are now believed to be degenerate forms that have lost adaptation for flight. Indeed, they resemble permanent overgrown chicks with short, stubby wings and soft rather than stiff-vaned flight feathers. This condition, in which animals reach adult size and maturity while maintaining an infantile appearance, is called neoteny. In their own environment, however, the ratites are by no means inferior to other birds. With their strong, heavy legs and reduced toes, they are powerful runners, and their heavy, solid bones are sturdier than the hollow bones of flying birds. The ratites include the Afro-Asian ostriches and their South American counterparts the rheas as well as a number of orders now or recently native to Australia, New Zealand, and New Guinea : the emus and cassowaries, the kiwis, the extinct moas, the Madagascan elephant birds, and several other extinct orders. The small, tropical New World tinamou has a keeled sternum and can fly, but shares some features with the ratites, such as the possession of a specialized bony palate. The flightless penguins are not ratites, since they have neither bony palate nor flat breastbone. In addition, their wings are powerful swim fins, and their chest muscles and sternum are as developed as those of any flying bird. The orders of ratites are classified in the phylum Chordata, subphylum Vertebrata, class Aves.
Ostriches (Struthio camelus) can be found in Africa and parts of SW Asia. They are the largest of living birds; some males reach a height of 8 ft and weigh from 200 to 300 lbs. The ostrich can run at great speed with it's wings outspread. The inner of the two toes on each foot is much larger and bears most of the bird's weight. The ostrich kicks when angered and can inflict serious injury. In both sexes the head, neck, and thighs are bare or scantily feathered. The male is glossy black with long white plumes on the wings and tail. The female is a dull grayish brown. Usually the polygamous male has from two to six females in his flock. The male ostrich scoops out a hollow for the eggs, which weigh nearly 3 lbs. One of the females incubates the eggs during the day, and the male takes over at night. Ostriches are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Struthioniformes, family Struthionidae.
The Rhea, common name for a South American bird of the order Rheiformes, superficially resembles the ostrich. Weighing from 44 to 55 lbs and standing up to 60 in. tall, the rhea is slightly smaller than the ostrich and lacks the birds extravagant plumelike tail feathers. The rhea also differs from the unrelated ostrich in structure of the palate, pelvis, and foot. It is yellow and gray above, with a black head and dirty-white underside. The common rhea is found from northeastern Brazil to Argentina. The somewhat smaller Darwin's rhea occurs from Patagonia to the high Andes. The rhea is typically a creature of the pampas and savannas and may often be found feeding in mixed herds along with cattle or guanaco, occupying an ecological niche similar to that of the ostrich and the zebra of Africa. Rheas feed on several kinds of plants, insects, and small vertebrates. While the old males tend to stay solitary, the young male is aggressive and highly polygamous, gathering about itself from three to seven hens. The nest is built in a dry and protected area, preferably near water. The male excavates a shallow hole with his bill, lines it with dry vegetable matter, and assumes all the incubation duties. He may incubate as many as 50 eggs, produced by a number of females over a period of weeks. Incubation takes from 35 to 40 days. The eggs weigh up to 2 lbs each. When hatched, the chicks are gray with darker stripes. Rheas are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Rheiformes, family Rheidae.
Emus are found in Australia. They are 5 to 6 ft tall and are very swift runners. The head and neck are feathered. The six or seven dark green eggs, laid in a sandy pit, are sometimes incubated by the male and require 56 days to hatch. There is only one living species, Dromiceius novaehollandiae. Emus are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Casuariiformes, family Dromiceidae.
Cassowary are swift-running, pugnacious forest birds of Australia and the Malay Archipelago. They are smaller than the ostrich and the emu. Their plumage is dark and glossy and the head and neck unfeathered, wattled, and brilliantly colored, with variations in the coloring in different species. The head bears a horny crest. The female is larger than the male, though both sexes are similar in color. They are monogamous and nest in shallow nests of leaves on the ground in forests. Only the male incubates the female's three to six eggs. Cassowaries are primarily nocturnal. Their diet consists mainly of fruits and berries, although some eat insects and small animals. Cassowaries are notoriously vicious and have attacked and killed men with their sharp, spikelike toenails. They are fast runners, attaining speeds up to 30 miles per hour. Cassowaries are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Casuariiformes, family Casuariidae.
Kiwis are the smallest members of the ratite. They are the size of a large chicken and have short, stout legs and coarse, dark plumage that hides their rudimentary wings. They lack wing and tail plumes and walk with a rolling gait. It is the only bird whose nostrils open at the tip of the bill, which is long, slender, and curved. Kiwis hide during the day and forage at night for grubs and worms. Their eyesight is poor; the long, hairy bristles at the base of the bill are believed to have a tactile function which is thought to supplement their keen sense of smell in hunting. Kiwis nest in underground burrows, the male performing the incubational duties. The one or two eggs take from 75 to 80 days to hatch. The three living species of kiwi, genus Apteryx, have dwindled with the advance of agriculture and the introduction of predators such as cats, weasels, and stoats, but they are now rigidly protected by law. Kiwis are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Apterygiformes, family Apterygidae.
The moa is an extinct flightless bird of New Zealand. The various species ranged in size from that of a turkey to the 13-ft Dinornis maximus. The bird had a short stout bill and was wingless : even the shoulder girdle was lacking in most species. Remains preserved in caves and bogs include bones, pieces of skin, feathers, and egg shells. Although the birds were hunted largely by the Maoris, the reason for the moas' extinction is not precisely known. It is estimated that there were 22 species of moas. Moas are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Dinornithiformes, family Dinornithidae.
Tinamou are South American game birds. They are protectively colored in browns and grays. The females are the aggressors in courtship, and the males incubate the colorful eggs and rear the young. Tinamou are similar in appearance to partridges. They are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Tinamiformes, family Tinamidae.