Type of animal science: Classification
Fields of study: Anatomy, ornithology, physiology, population biology
The ostrich and its relatives are famous for their exotic appearance and for being flightless birds. They are the oldest type of bird alive today, dating back eighty million years to the age of dinosaurs.
Principal Terms molt: to shed old feathers and grow new ones monogamous: having only one mate nomadic: travels distances in search of food omnivorous: eating both animal and plant foods polygamous: having more than one mate precocial: in birds, those that are down-covered, fully developed, and active at birth
Ostriches belong to a striking group of flightless birds known as ratites, that also includes emus, cassowaries, rheas, and kiwis. Ratites have flat, smooth breastbones that lack a keel to which flight muscles could attach. They are thus unable to fly, and have weak wing muscles. They do use their wings, spreading them out to help them cool off, and also to splash water when bathing. Ratite feathers are different from those of flying birds. The individual strands are not interlocked, and thus they are soft and billowy and air passes right through them. Their plumes have long been admired by humans and used for decoration and adornment. As with other birds, their feathers function as protection from the elements, and ratites preen, spreading waterproofing oil to their feathers with their beaks. They also molt once a year. Ratites have heavy, strong bones and powerful leg muscles, and are able to run swiftly. They are omnivores, feeding on a variety of grasses, plants, seeds, fruit, insects, and small animals. There are many farms in the United States that raise ostriches, emus, and rheas for their feathers, hide, meat, and oil. In their native countries, ratites are hunted or raised for their feathers and as food. Ostriches have also been tamed for riding and for pulling carts.
Ostriches have long necks and legs and are the largest living birds. Males stand eight feet tall, and weigh three hundred pounds. The ostrich can take strides of twenty-five feet and outrun pursuers at speeds of forty miles per hour. If cornered, the ostrich has a powerful kick that can maim an enemy. It has two toes on each foot, and a razor-sharp toenail that both grips the ground while running and can slash the flesh of its enemy.
Male ostriches are black with white plumes on their tail and wings. Females are grayish-brown. The head and legs are featherless. The neck is covered with down and is red or grayish. The ostrich has huge eyes with long protective lashes and has keen eyesight for spotting danger a long way off. It can make loud hissing and roaring noises.
Ostriches are native to Africa; they are nomadic and graze on open savanna. They often follow herds of zebras or antelope, catching insects and small animals stirred up by their hooves. They swallow sand and stones to help grind up their food. Contrary to popular belief, they require a regular water supply.
When mating, male ostriches make a booming call and perform a courtship dance for the females. They are polygamous, taking three or more
Ostriches and related birds
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Aves
Orders: Struthioniformes (ostriches); Casuariiformes (emus, cassowaries); Rheiformes (rheas); Apterygiformes (kiwis) Families: Struthionidae (ostriches, one genus, six species); Dromaiidae (emus, one genus, three species); Casuariidae (cassowaries, one genus, four species); Rheidae (rheas, two genera, nine species); Apterygidae (kiwis, one genus, seven species) Geographical location: Southern Hemisphere—Africa (ostrich), Australia (emu and cassowary), New Guinea (cassowary), South America (rhea), New Zealand (kiwi) Habitat: Semidesert and open plains (ostrich, emu, rhea); forests (cassowary, kiwi)
Gestational period: One breeding cycle per year; incubation varies from forty days (ostrich) to eighty days (kiwi) Life span: Ostriches average forty years in the wild, up to eighty years in captivity; others average ten to twenty years Special anatomy: Unkeeled breastbone, tiny wings, unbarbed feathers, solid bones, strong muscular legs hens as mates. The male scratches a shallow pit into which each female lays up to a dozen eggs, for a total clutch size of up to thirty eggs. This communal nesting behavior is unusual among birds. The male shares incubation with one dominant female. The male sits at night and the female during the day. Ostriches lay the largest eggs of all living birds, seven inches long and three pounds. The eggshell is very tough and hard for predators to crack open. The parent will sometimes lay with its neck outstretched on the ground when danger threatens, giving rise to the legend that they bury their heads in the sand. They may also feign injury to lure predators away from the nest. Newborn chicks are precocial and instinctively know how to search for food. They are full adults by three years of age.
Rheas live in flocks on grasslands in South America. They are similar to ostriches in behavior and appearance, although they have three toes on their feet, as do most of the other ratites. They are brownish in color and can be five feet tall. They are polygamous, but only the male incubates the eggs.
Emus live on plains in the Australian outback, and flock nomadically according to rainfall patterns and the resulting food supply. The emu is the second largest flightless bird, nearly six feet tall and eighty-five pounds. It has brown feathers and a loose, moplike tail. Emus are monogamous.
Cassowaries live in the rain forests of New Zealand and northeastern Australia. They are solitary and territorial, pairing only to mate. They feed primarily on fruit fallen from trees. Cassowaries have black, loosely hanging feathers, and the wings are composed only of quills. They have bright blue heads and colorful wattles. A distinctive bony crown on the head called a casque helps them push through the dense forest, and is also used to turn over litter in search of food.
Kiwis are elusive, nocturnal birds that live in the forests of New Zealand. They are the smallest ratites, about the size of a chicken. They have round, brown-feathered bodies, short legs, four toes, and run by placing one foot directly in front of the other. Their long, slender beaks have nostrils at the very tip, and are used to probe the ground to locate worms, beetles, spiders and larvae by smell. Males have a shrill, whistling mating call. Females lay only one or two eggs that are enormous in proportion to their body size.
—Barbara C. Beattie See also: Birds; Fauna: Africa; Fauna: Australia; Fauna: South America.
1178 • Ostriches and related birds
Arnold, Caroline. Ostriches and Other Flightless Birds. Minneapolis: Carolrhoda Books, 1990. A good introduction for the intermediate reader that focuses mainly on ostriches.
Baskin-Salzberg, Anita, and Allen Salzberg. Flightless Birds. New York: Franklin Watts, 1993. Covers all flightless birds for the juvenile reader, clearly explaining ratite characteristics with a section on each type.
Deeming, Denis C., and D. Charles Deeming, eds. The Ostrich: Biology, Production and Health. New York: Oxford University Press, 1999. A state-of-the-art presentation on the raising of ostriches, written by specialists from academia and industry.
Drenowatz, Claire, ed. The Ratite Encyclopedia: Ostrich, Emu, Rhea. San Antonio: Ratite Records, 1995. Provides in-depth information on ratite anatomy and physiology as well as the various aspects of ratite farming, such as rearing, farm design, and record management.
Gould, Stephen Jay. "Tales of a Feathered Tail." Natural History 109, no. 3 (November, 2000): 32-42. An insightful discussion of the evolutionary theory regarding the descent of flightless birds from dinosaur ancestors.
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