Monitoring breeding outcomes of cryptic nocturnal species such as the North Island brown kiwi (Apteryx mantelli) is an important aim for conservation management in New Zealand. While fitting male kiwi with radio transmitters enables incubation burrows to be found and monitored, it is invasive and expensive. Remote monitoring methods (without handling of birds) are preferable.
This study investigated how predation risk in North Island brown kiwi changes as the birds grow and develop. Over a 10-year period, 53 adult and 126 young kiwi were radio-tagged at Lake Waikaremoana and studied to determine survival rates, causes of death, and rates of growth. Predation loss amongst adults was low (2.49% year-1) and caused mainly by ferrets. Young kiwi suffered intense predation from stoats during their first four months of life, but thereafter became too large (> 800 g) for stoats to kill.
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.