North Island Brown Kiwi
Order: Apterygiformes
Family: Apterygidae
Genus/Species: Apteryx mantelli
Description: The nocturnal
flightless North Island Brown Kiwi is so remarkably unbirdlike in appearance
and behavior that is has sometimes been referred to as an
"honorary mammal." The kiwi's "fur" is
actually a thick covering of shaggy hairlike grey-brown feathers.
The useless vestigial wings (4-5 cm long) are completely hidden
under the plumage. They have no external tails. The wide spacing
of their robust sharp-clawed legs gives them an amusing rolling
gait. Kiwis are stout birds, standing 50 cm tall with females
(2,060-3,850 grams) weighing up to 30 percent more than males (1,440-3,060
grams).
Most of the world's birds have excellent eyesight and a poor to non-existent sense of smell. Kiwis reverse this usual arrangement. It is estimated that they can see only two feet ahead of them in daylight, and six feet at night. The kiwi's long (up to 20 cm) pale grey-brown bill is unique in the bird world in having the nostrils located near the tip. They smell their prey rather than see it. A few feathers around the base of the bill are highly modified to form long tactile bristles. These rictal bristles help the bird feel its way around in the dark, compensating for the relatively poor eyesight. Though their eyes are small, their ears are unusually large.
The name kiwi is derived from the ringing call of the male. Females respond with a hoarse throaty call which has been likened to the sound caused by opening an extremely old rusty barn door. These calls allow the pair to mark their territories and remain in contact while foraging separately. Both sexes can produce an assortment of grunts, growls, and hisses and often snuffle audibly when searching for food. The snuffling may be produced by the opening and closing of a valve behind the nostrils that prevents the bird from inhaling dirt and debris as it probes the soil and leaf litter.
Distribution and Habitat: There are five kiwi species: the North Island Brown Kiwi, Great Spotted Kiwi, Lesser Spotted Kiwi, Rowi, and Tokoeka. All are endemic to New Zealand. The National Zoo exhibits the North Island Brown Kiwi. These kiwis are found from sea level to 1,200 meters. Their original habitat was moist coniferous forest dominated by kauri and tree-ferns. Clearing of much of this primeval forest has forced many kiwis to attempt to survive in partially timbered agricultural areas. The largest remaining population of Brown Kiwis on North Island resides in a large commercial pine plantation.
Kiwis form life-long pair bonds and exhibit remarkable fidelity to their home territories. They will remain in a territory for weeks after every tree has been logged. Territories range in size from five to 50 hectares depending on the quality of the habitat. Kiwis excavate several burrows within each territory. A typical underground burrow has one entrance, a tunnel 20 to 200 cm in length and a terminal chamber large enough to accomodate both birds. They will also utilize hollow logs or shallow holes dug out between tree roots.
Diet: Brown Kiwis have an extremely varied diet which includes earthworms, beetles, snails, crayfish, insects, fruits, and berries. The unique bill is used to sniff out food as the bird forages by plunging it repeatedly into the leaf litter of the forest floor in search of prey. They forage actively from dusk to dawn.
Reproduction: Kiwi nests are usually located in well established burrows where the surrounding foliage has had time to grow up and thoroughly conceal the entrance. The female Brown Kiwi lays one or two glossy white eggs of prodigious size, 14-20 percent of her body weight. Producing such a large and energy rich (more than 60 percent yolk) egg depletes the females energy reserves. There is a period of 25 to 30 days between the laying of the first and second egg. It is entirely understandable that she leaves the male alone in the nest burrow to handle the 70- to 80-day incubation by himself.
Kiwi chicks have no egg tooth and must use their feet to kick their way out of the shell. A newly hatched kiwi looks like a mini replica of the adult, at 1/8 adult size. They are precocial chicks, able to forage for themselves with only minimal paternal supervision for their first few days of life. Although completely independent by two weeks of age, they do no reach adult size until they are 18 to 20 months old.
Conservation: Kiwis have long been the cherished national mascot of New Zealand. Though they have enjoyed complete legal protection since 1896 and large tracts of pristine forests have been set aside in parks and reserves, their numbers are dropping by 5.8 perecnt each year. In 1996 scientists estimated the North Island Brown Kiwi population at 35,000 birds. They predict that if current trends continue that number will drop to 20,000 by the year 2006. Kiwi populations have been on this downward slide ever since humans arrived in New Zealand more than a thousand years ago.
New Zealand is one of the most isolated large island groups in the world. There had been no large predators on the islands of New Zealand between their separation from the other continental land masses of Gondwanaland at the end of the Cretaceous period, 130 to 80 million years ago, and the arrival of the first human settlers. The only native land mammals were two species of small bats. Many birds lost the power of flight in response to the absence of significant predators. There were two orders of ratites, flightless birds, endemic to New Zealand; the Apterygiformes (kiwis) and the Dinornithiformes (moas). The moas, diurnal grazers and browsers occupying scrubland and forest edges, were divided into 13-29 species. They ranged in size from that of a domestic turkey to one species that stood taller than three meters and weighed 350 kg.
Around 1000 CE the Maoris, settlers from East Polynesia, were the first humans to reach New Zealand. They brought with them the domestic dog and the Polynesian rat. Maoris actively hunted the native birds and burned the lowland forests to clear land for their sweet-potato-based agriculture. The combination of intensive hunting pressure and large-scale deforestation drove all of the moas and several other species of flightless birds to extinction. Although the kiwis' smaller size, nocturnal habits, and preference for deep-forest habitat made them less vulnerable than their larger cousins the moas, they began to disappear from portions of their historic ranges. This process of range constriction continued with the arrival of European settlers in the 19th century.
Europeans introduced a variety of additional predatory species, both deliberately and accidentally. From domestic dogs and cats to stoats, weasels, ferrets, bushy-tailed possums and rats, they all have taken their toll on the numbers and reproductive success of the ground-nesting kiwis. Stoats alone kill 60 percent of all Brown Kiwi chicks hatched each year. A single dog is believed to have killed 500 of the 800 kiwis estimated to reside in the Waitangi Forest on North Island in under two months. While adult kiwis are usually feisty enough to defend themselves against the smaller predators, their eggs and newly hatched young are extremely vulnerable to predation.
Massive education campaigns are involving the entire New Zealand population in the fight to save their national emblem. Rural residents contribute to conservation efforts by keeping their dogs contained and monitoring kiwi populations in their neighborhoods. Farmers are asked to fence their stock out of critical kiwi habitat to prevent forest degradation. Foresters are asked to refrain from burning brush off of newly cleared lands to avoid burning the resident kiwis who are often reluctant to leave their territories even after all the trees are gone. If they must burn they are encouraged to wait at least two months after cutting to allow kiwis time to move on. Both farmers and foresters are participating in the control of the introduced pest species. The New Zealand Department of Conservation has recently initiated a five-year $6.6 million program to research better stoat eradication techniques.
Conservationists are working to establish predator-free reserves on off shore islands and fenced areas to function as safe population reservoirs. Operation Nest Egg collects kiwi eggs from the wild to be reared in captivity or on these predator free reserves. The birds are reintroduced into their native forests when they are large enough to defend themselves from stoats and other small predators. This program has increased chick survival rates from five to 85 percent. Reintroduced birds are being monitored to learn whether they will be able to reproduce successfully.
Brown Kiwis at the Zoo: The Bird House has two males on exhibit. Because kiwis are nocturnal, they are exhibited in a reversed-schedule room. Their "night" occurs during the day so that visitors can observe them as they moves about his enclosure. Zoo visitors can get a closer view of one of these secretive birds at 11 a.m. on Mondays, Wednesdays, and Fridays when a hand-reared kiwi is brought out to meet the public.
References:
Austin, O. 1961. Birds of the World. Golden Press. NewYork.
Bank of New Zealand Kiwi Recovery Programme (May, 1999). Available at: http://www.savethekiwi.org.nz
Cassels, R. 1984. The Role of Prehistoric Man in the Faunal Extinctions of New Zealand and Other Pacific Islands. In Quarternary Extinctions (P.S. Martin and R.G. Klein eds), pp. 741-767. The University of Arizona Press, Tuscon, Arizona.
Del Hoyo, J., Elliot, A. and J. Sargatal. eds. 1992. Handbookof the Birds of the World. Vol. 1. Ostrich to Ducks. LynxEdicions, Barcelona.
Falla, R.A., Sibson, R.B. and E.G. Turbott. 1978. Birds of New Zealand. New Zealand Ornithological Society.
