Kiwi have declined markedly in abundance and range since human settlement of New Zealand. Three of the four species are still extant in mainland forests, despite decades of co-existence with various introduced mammals. Little spotted kiwi is now probably confined to offshore islands. The role of introduced mammals in these population declines was evaluated by measuring the survival rates of adults, eggs and chicks of brown kiwi (A. mantelli) and great spotted kiwi (A. haastii) in mainland forests.
Historical and recent records indicate that kiwi are less numerous and widespread in Hawke's Bay than they used to be. The birds are still scattered throughout the ranges to the west and north of the region, usually at densities of about one bird per 100 ha. Kiwi have now almost completely disappeared from their former lowland habitats. The decline of kiwi in Hawke's Bay may have started before European settlement, but has been particularly rapid in the last 70 years. RePeat surveys of three populations between 1984 and 1990-91 indicate that the decline is continuing.
Incubation temperatures of the great spotted kiwi were studied by telemetry methods at the Otorohanga Zoological Society in October 1989. The male maintained the core temperature of the egg at about 28-31.8-degrees-C. When he emerged to feed at night, the female started to incubate. She did not have a brood patch, but could heat the egg to 28-28.5-degrees-C, sufficient for embryo growth. Some of the reasons why female great spotted kiwi might help with incubation are discussed.
Twenty-three kiwi were radio-tracked for 16-116 weeks in a Northland reserve. Eighty-three percent of the kiwi made use of the numerous forest remnants scattered over farmland outside the reserve. All remnants isolated by up to 80 m of pasture were used by kiwi. The maximum distance kiwi walked between forest remnants was 330 m. Longer migrations of up to 1.2 km from the reserve were made by kiwi using small forest remnants as 'stepping stones'.
Three pairs of kiwis were fitted with radio transmitters and followed for two years in a forest remnant in Hawke's Bay. Laying began in late June or July, when both sexes reached peak weight, and usually finished in November. Twelve of 14 nests were in burrows, 470-900 mm long. Females laid 2-5 eggs each season, 21-60 days apart; clutches which failed in the first few weeks of incubation were replaced. Completed clutches comprised two eggs. A second clutch laid after the first had successfully hatched was recorded only once.
Twelve kiwis were radio-tagged and tracked for 12-78 weeks in two sites in Hawke's Bay. Four bonded pairs had ranges of 19.1 to 42.3 ha (estimated by the convex polygon method), which were apparently defended against other kiwis. Two unmated females had ranges of 48.0 and 43.1 ha. Another unmated female occupied a narrow, circular strip, 5.4 km long, covering about 26 ha. The ranges of four kiwis in scrubland and eight in climax beech/podocarp forest were similar in size.