Ostrich: Struthionidae

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OSTRICH: Struthionidae

PHYSICAL CHARACTERISTICS

Ostriches are ratites, flightless birds that have a flat breastbone rather than a keeled or curved breastbone like birds of flight. They have a simple wing bone structure, strong legs, and no feather vanes, making it unnecessary to oil the feathers. Therefore, ostriches have no preen gland that contains preening oil.

Ostriches are the largest birds in the world, with long legs and necks. They range in height from 5.7 to 9 feet (1.8 to 2.8 meters) and weigh from 139 to 345 pounds (63 to 157 kilograms). They have loose-feathered wings. Males have black and white feathers while females have grayish brown feathers. They have powerful legs, each with two toes. One of their two toes has a strong 4-inch (10-centimeter) claw while the other toe is usually clawless.

There are four living subspecies of ostrich: North African, Somali, Masai, and South African. Skin color is usually light but varies among subspecies, including pink in the North African ostrich and blue in the Somali ostrich.

GEOGRAPHIC RANGE

Ostriches are found in parts of central and southern Africa.

HABITAT

Ostriches live in dry, sandy regions of Africa, including grassland, desert, woodlands, shrubland, and savannas, flat grasslands with scattered trees and shrubs.

DIET

Ostriches are omnivores, meaning they eat both plants and animals. Their primary diet includes grasses, shrubs, seeds, roots, leaves, flowers and sometimes locusts and grasshoppers. However, they will on occasion eat small animals, such as lizards and mice, and animal remains. Ostriches also eat sand and small stones that help grind up food in their digestive systems. Their intestines are 46 feet (14 meters) long, allowing food to remain in their systems a long time in order to absorb a maximum amount of nutrients from their food.

BEHAVIOR AND REPRODUCTION

Ostriches are diurnal, meaning they are most active during the day. They are sometimes active on moonlit nights. They live in flocks, families and alone. The flocks can range in size from five to fifty birds and are usually found grazing with other herbivores, including antelope and zebras. During the breeding season, flocks occupy territories of 0.8 to 6 square miles (2 to 15 square kilometers). Flocks often gather together, forming large groups of hundreds of birds. Outside the breeding season, flocks are usually much smaller, generally two to five birds but sometimes up to ten birds. Male ostriches are called cocks and females are hens.

Ostriches take frequent sand baths, especially during dry periods, laying together in large sandy depressions where they stir up the sand with powerful wing beats. They also like to take water baths, and do so frequently during the wet season when pools of water are more plentiful.

HEADS UP

It is a myth that ostriches, when frightened, will hide their heads in a hole or bury them in the sand. Often, when they feel they are in danger, ostriches will try to escape detection by laying flat on the ground with their necks and heads outstretched. Since the head and neck are usually a light color, they blend in well with the dirt and sand. From a distance, only the body is readily visible and it is believed this behavior gave rise to the myth.

The normal walking pace of ostriches is 2.5 miles per hour (4 kilometers per hour). When ostriches sense danger or are threatened, they can run at speeds of up to 45 miles per hour (70 kilometers per hour) for a few minutes and can maintain a steady speed of about 31 miles per hour (50 kilometers per hour) for thirty minutes. Ostrich strides can be 10 to 16 feet (3 to 5 meters). When running, ostriches hold their wings out for balance, especially when making sudden turns. Ostriches prefer to outrun their predators but when cornered, they will use their long and thick legs as weapons. An ostrich's kick is so powerful, it has been known to kill lions.

Ostriches have a wide variety of vocal sounds, including whistles, snorts, and grunts. They have a loud booming call used to announce their territory.

Ostriches are territorial, meaning they are protective of an area they consider home and claim exclusively for themselves. Each family has its own territory, which is established by the dominant male. The family also has a dominant female and several other females, called minor hens. During the mating season, a male will show its dominance by stretching its head high and lifting its wing and tail feathers. Ostriches of both sexes show submission by holding their heads, wings, and tails towards the ground.

Males and females are polygamous (puh-LIH-guh-mus), meaning they have more than one mate at the same time. Following mating, the dominant male will build a nest by scraping the ground or sand with his feet several times, making a shallow depression. A number of females will lay their eggs in a single nest. The dominant hen is the first to lay eggs. She will lay up to twelve eggs in the center of the nest over a three-week period. The minor hens will then lay their eggs around the dominant hen's eggs. Ostrich nests usually contain thirteen to twenty eggs but can contain up to sixty eggs. On average, one egg is 6 inches (15 centimeters) long and 5 inches (13 centimeters) wide and weighs 3 pounds (1.4 kilograms). Often, after all the eggs are deposited, the dominant female will discard some of the eggs laid by the minor hens. The dominant male sits on the eggs at night and the dominant female during the day. The eggs take about forty-two days to hatch. About 10 percent of the eggs will hatch and on average only one chick per nest will survive to adulthood. The average lifespan of an ostrich is thirty to forty years but can be up to fifty years, both in the wild and in captivity.

OSTRICHES AND PEOPLE

The documented relationship between ostriches and humans dates back 5,000 years to Mesopotamia and Egypt, where ostriches were raised for their feathers, eggs, skin, and meat. Ostriches are still used for these purposes but are raised on commercial farms in Africa, Europe, and North America. Their eggs are used both as food and for decoration.

CONSERVATION STATUS

Ostriches are not listed as a threatened species by the World Conservation Union (IUCN). The subspecies known as the Arabian ostrich is believed to have become extinct, no longer existing, in the 1940s. Ostriches were common in most of Africa and southwest Asia until about 100 years ago. Ostrich populations began declining about 300 years ago when their feathers became fashionable and hunting was widespread. By the early 1800s, ostriches were nearly extinct and farms were established in Africa to raise them. Although they survived extinction, their numbers are limited. They are found mostly in national parks, game preserves, and commercial farms.

FOR MORE INFORMATION

Books:

Davies, S. J. J. F., et al. Bird Families of the World. Vol. 8, Ratites and Tinamous: Tinamidae, Rheidae, Dromaiidae, Casuariidae, Apterygidae, Struthionidae. Oxford, U.K.: Oxford University Press, 2002.

Elwood, Ann. Ostriches, Emus, Rheas, Kiwis, and Cassowaries. Mankato, MN: Creative Education, 1991.

Harris, Timothy. Ostriches, Rheas, Cassowaries, Emus, and Kiwis. New York: Beech Publishing House, 1997.

Sinclair, Ian, et al. Birds of Southern Africa. Princeton, NJ: Princeton University Press, 2002.

Zim, H. S. Ostriches. New York: William Morrow, 2000.

Periodicals:

Manilus, N. "The Ostrich in Egypt: Past and Present." Journal of Biogeography (August 2001): 945–953.

Ostrowski, S., et al. "Evidence of a Dramatic Decline of the Red-Necked Ostrich Struthio camelus camelus in the Air and Tenere National Nature Preserve, Niger." Oryx (October 1, 2001): 349–352.

Potts, D. T. "Ostrich Distribution and Exploitation in the Arabian Peninsula." Antiquity (March 2001): 182.

Thompson, Rebecca S. "Raising Emus and Ostriches." United States Department of Agriculture Special Reference Brief, No. SRB 97-06. (November 2000).