The Brown Kiwi population is estimated at 25,000, of which about 8000, of these tough, stroppy, spiky feathered birds survive in the Northland region. While mainland populations are declining at a rate of 4 - 5 per cent each year, where active predator or breeding management is being carried out their numbers are stable or increasing.
Kiwi prefer lowland and coastal indigenous forest, but the huge changes to New Zealand's original forest cover mean the kiwi have to be adaptable. Today they live in many different types of vegetation, including exotic forests and rough farmland.
The size of the kiwi's territory can range from 2 to 100 hectares depending on their food supply of insects and berries in any given area, and the males are fiercly territorial.
The original absence of mammal predators for kiwi allowed them to make their homes in many different environments, from snowy tussock lands to sand dune burrows, from mossy forest floors to rough grassland.
The Brown Kiwi sleeps and nests in simply constructed, one entrance burrows, it may be dug in the earth of a bank or slope, using their strong legs and claws to loosen the earth and push it out and away from the entrance. Or their day shelter may be in a hollow tree, under a log, in a rock crack or within a dense clump of vegetation.
Kiwi are prolific breeders and usually mate for life, regularly producing huge eggs. Take away the predators, and kiwi could be successful once again. Their eggs are one of the largest in proportion to body weight of any bird in the world. In Northland they produce their eggs at any time during the year. The incubation period is about 75 days, and the male predominantly takes the nurturing role during this time. When they hatch kiwi chicks are mini-adults fully feathered and open-eyed, and after 5 days leave the burrow to forage for themselves. After 5 weeks they may leave the area seek their own territory.
During its first three-to-four weeks, the baby kiwi feeds at night, and sometimes during the day. This makes it extremely vulnerable to predators. Around 90 per cent of kiwi chicks born in the wild die within their first six months - 70 per cent of them killed by stoats and cats. Only about five per cent of kiwi chicks survive to adulthood. Those that do survive may live to their 60s.