North Island Brown Kiwi(Apteryx mantelli)
The North island brown kiwi is a flightless nocturnal bird. Its plumage is streaky red-brown and spiky. It has a long and curved bill with the nostrils located near the tip. This unique adaptation helps the kiwi during foraging because it locates its prey by smell rather than by sight. Females stand about 40 cm high and weigh about 2.8 kg the males about 2.2 kg. The North Island brown kiwi is the only species of kiwi found internationally in zoos.
Habitat
They are widespread throughout the North Island, occurring near Northland, Coromandel, Eastern North Island, Aroha Island, Little Barrier Island, Kawau Island, Ponui Island, and the Whanganui Region. These birds have demonstrated a remarkable resilience to adapt to live on scrub-like farmland, pine (an introduced tree) plantations, and their native forests, however, they still prefer dense, sub-tropical and temperate forests. The range is indicated by the brown colour on the map adjacent to this.
Diet
They are carnivores. Their diet includes earthworms, beetles, snails, crayfish, insects, crayfish, amphibians, and eels. They will also sometimes eat fruits and berries.
Breeding
They are monogamous and form pairs that can mate for life. They may produce 2-3 clutches a year. The nest is located in a burrow dug in the ground. The female lays 2 eggs and the male incubates them for 75-90 days. The chicks are precocial and hatch fully developed. They leave the nest within 1 week after hatching and are able to feed themselves. They usually become independent at 4 weeks of age and reach reproductive maturity when they are 4 years old.
Population
According to the IUCN Red List, they are classed as Vulnerable(VU). In 2015, the estimated number of individuals in the four main populations was: 8,200 in Northland, 1,000 on Little Barrier, 1,700 on the Coromandel Peninsula, 7,150 in the eastern North Island and 7,500 in the western North Island, giving a total of 25,550 birds. More than 1,000 individuals of this species are also present on pest-free offshore islands, especially Hauturu-o-Toi/Little Barrier. The total population is therefore estimated to number 26,550 (rounded here to 26,600), which equates to approximately 17,700 mature individuals, placed here in the band 10,000-19,999 mature individuals. Unmanaged mainland populations are declining at 2.5% per annum owing to introduced predators. However, this is thought to be balanced by population increases in areas where predators are absent or managed to low densities. It is estimated that the population has undergone an overall reduction of 30-49% across three generations (26 years). At the moment their population is considered to be stable.
Threats
The most significant threat to the survival of the species is predation of adults by dogs and ferrets, with predation of young kiwi by Stoat and cats also affecting populations. Significant spikes of mortality can occur, for example, a single dog killed 500 birds in six weeks (over 70 incidents of dogs killing kiwi in Northland occurred between 1990 and 1995. The smaller male kiwi may be at greater risk of predation by ferrets, resulting in a skewed sex ratio and reduced effective population size. In one population prior to management at least 94% of chicks died before reaching breeding age. About half were killed by introduced predators, in particular, stoat and cats. Juvenile kiwi become too large for stoats above about 800g, which takes about four months to achieve. The clearance of habitat fragments continues to threaten small populations, but the rate of loss of native habitat has declined markedly and this is not currently considered a driver for population reductions. New avian diseases and pathogens are a potential threat, particularly with the importation of non-native but closely related ratites to New Zealand.
Conservation
Conservation and research actions underway
Monitoring is intensive and nationally coordinated, and uses call-counts, specially-trained dogs searching for banded birds, and radio-tracking. Key populations are managed by controlling predators by the use of trapping and poisoned baits, with leg-hold predator traps that are raised above the ground to prevent accidental trapping. Kiwi aversion training for hunters' dogs is being trialed, although there is no evidence that this is a viable long-term solution. A programme of removing and incubating eggs and returning subadults once these are large enough to fend off predators has been developed since 1995 under the name Operation Nest Egg. A dedicated rearing facility was constructed at which 942 eggs received from the wild produced 475 young released back into the wild between 1995 and 2008, with survival in captivity greatly improving during this time. BNZONE has been demonstrated to be the most effective tool for the species, resulting in a 12.5% annual population increase within managed sites, due to 83% chick survival. Due to the cost and need to locate nests this approach is only practical within areas up to 10,000 ha and should be used to turn around declines in the most threatened and restricted populations and subspecies. Many national and overseas captive populations are held.
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Conservation and research actions proposed
Carry out landscape-scale pest control at sufficient intervals at the sites that are currently unmanaged, specifically for mustelids, rats, cats and dogs. Intensively manage at least one population of each regional taxon using the BNZONE programme to increase the population size. Undertake population modelling for all taxa. Investigate landscape-scale remote monitoring techniques for sparse populations. Promote legislative and policy changes to protect populations and encourage high-quality advocacy at all levels. Educate and inform the public and encourage community involvement in Kiwi conservation.