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Flightless Birds

Kiwis

Kiwis are three species of small, forest-dwelling, flightless birds that live only in New Zealand. The body length of kiwis ranges from 14-21 in (35-55 cm), and they typically stand about 15 in (38 cm) tall. Adult birds weigh 3-9 lb (1.5-4 kg). Kiwis have a rounded body with stubby, rudimentary wings, and no tail. Their legs and feet are short but strong, and they have three forward-pointing toes as well as a rudimentary hind spur. The legs are used in defense and for scratching about in the forest floor while feeding.

The bill is long, flexible, slightly down-curved, and sensitive; it is used to probe for earthworms and insects in moist soil. Their nostrils are placed at the end of the beak. Kiwis appear to be among the few birds that have a sense of smell, useful in detecting the presence of their invertebrate prey. They snuffle as they forage at night, and their feeding grounds are recognized by the numerous holes left by their subterranean probings.

Kiwis have coarse feathers, which are hair-like in appearance because they lack secondary aftershaft structures, such as barbules. Their shaggy plumage is brown or gray. The sexes are similar in color, but the female is larger than the male.

Kiwis lay one to two eggs, each of which can weigh almost 1 lb (0.5 kg), or about 13% of the weight of the female. Proportionate to the body weight, no other bird lays an egg as large. The female lays the eggs in an underground burrow—a cavity beneath a tree root, or a fallen log. The male then incubates them. The young do not feed for the first six to twelve days after hatching, and they grow slowly thereafter. Kiwis reach sexual maturity at an age of five to six years.

Kiwis are solitary, nocturnal birds. Because of the difficulties of making direct observations of wild kiwis, relatively little is known about these extraordinary birds. Kiwis make a variety of rather simple whistles and cries. That of male birds is two-syllabic, and sounds like" ki-wi." Obviously, this bird was named after the sound that it makes.

The brown kiwi (Apteryx australis) is the most widespread species, occurring in moist and wet native forests on South and North Islands, New Zealand. The little spotted kiwi (Apteryx oweni) is a gray-colored bird, while the great spotted kiwi (A. haasti) is more chestnut-colored, and larger.

Kiwis are the national symbol of New Zealand, and New Zealanders are commonly known as "kiwis." However, because these birds are nocturnal and live in dense forest, relatively few human kiwis have ever seen the feathered variety. Unfortunately, kiwis have suffered severe population declines over much of their range. This has been caused by several interacting factors. First, like other flightless birds (such as the extinct moas of New Zealand), kiwis were commonly hunted as food by the aboriginal Maori peoples of New Zealand. The feathers of kiwis were also used to ornament the ceremonial flaxen robes of the Maori. After the European colonization of New Zealand, settlers also hunted kiwis as food, and exported their skins to Europe for use as curiosities in the then-thriving millinery trade.

The excessive exploitation of kiwis for food and trade led to a rapid decline in their populations, and since 1908 they have been protected by law from hunting. However, some kiwis are still accidentally killed by poisons set out for pest animals, and they may be chased and killed by domestic dogs.

Kiwis have also suffered greatly from ecological changes associated with introduced mammals, especially species of deer. These invasive, large mammals have severely over-browsed many forests where kiwis live, causing habitat changes that are unfavorable to the bird, which prefers dense woody vegetation in the understory. Deer are now regarded as pests in New Zealand, and if these large mammals were locally exterminated, this would markedly improve the habitat available for kiwis and other native species. Fortunately, the conservation efforts of the government and people of New Zealand appear to be successful in their efforts to increase numbers of kiwis. These birds are now relatively abundant in some areas.

Resources

Books

Arnold, Caroline. Ostriches and Other Flightless Birds. Minneapolis: Carolrhoda, 1990.

Baskin-Salzberg, Anita, and Allen Salzberg. Flightless Birds. New York: Franklin Watts, 1993.

Forshaw, Joseph. Encyclopedia of Birds. New York: Academic Press, 1998.

Green, Carl R., and William R. Sanford. The Ostrich. New York: Crestwood House, 1987.

Ostriches, Emus, Rheas, Kiwis, and Cassowaries. San Diego: Wildlife Education, Ltd., 1990.


Jean F. Blashfield
Bill Freedman

KEY TERMS

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Barb

—The branches of a feather, growing out of the quill and sometimes held together by hooked barbules. Ratites' barbs are not held together.

Barbule

—Hooks that hold the barbs of a feather together in flying birds.

Casque

—The triangular bony growth that projects from the skull of a cassowary and stretches down over half the beak.

Keel

—The ridge on the breastbone of a flying bird to which flying muscles are attached.

Nictitating membrane

—A membrane that can cover the eye of some animals, in addition to the regular eyelid. It provides protection but still allows the animal to see.

Quill

—The central shaft of a feather, generally hollow, from which the barbs grow.

Additional topics

Science EncyclopediaScience & Philosophy: Ferroelectric materials to Form and matterFlightless Birds - Ostriches, Rheas, Emus, Cassowaries, Kiwis