Successes and failures
New Zealand Biodiversity Strategy
4 January 2004
The New Zealand Biodiversity Strategy Third Annual Report 2002/03 provides good and bad news of intensive kiwi management at three North Island and two South Island sanctuaries.
The Whangarei (Northland), Moehau (Coromandel) and Tongararo Forest sanctuaries in the North progressed well, exceeding target chick survival levels. Stoat trapping has been effective in enhancing recovery in these sanctuaries.
The managing agency, the Department of Conservation, reports that "...Whangarei saw a robust breeding season and 24 chicks were hatched and monitored. At Moehau, 14 of 18 chicks survived and none were killed by stoats - well above performance targets. At Tongararo Forest 19 chicks were raised using Operation Nest Egg (where eggs are removed and the chicks hatched and reared in a safe environment before being released back into the forest)..."
According to DoC, "... at Okarito just two chicks survived (after removal from the sanctuary) owing to a plague of stoats which killed the other monitored chicks. Despite very high catch rates of stoats, predation levels could not be reduced ..."
The Okarito kiwi, now called rowi, was scientifically described in 2003 as a distinct species Apteryx rowi. It is the most critically endangered kiwi, with a population of less than 200 birds restricted to 12,000 hectares in the Okarito Forest in Westland National Park.
According to DoC, adult survival is exceptionally high, with life expectancy at Okarito of more than 56 years.
"At the Haast tokeaka sanctuary only two chicks were produced due to poor laying and hatch rates (both survived). The use of Operation Nest Egg is being investigated to increase chicks numbers more quickly"
A plague of stoats at Okarito during the 2002/03 season was brought about by a plentiful food supply from the fruiting of rimu and kahikatea. The fruiting process known as "masting" provides a proliferation of seeds every five years.
It is a plentiful food source that causes an increase in rats, which are eaten by stoats.
The DoC project manager of the Okarito sanctuary, Jo Crofton, said "by Christmas day we had only two radio-tagged chicks left. I went out on Boxing Day to check on one of them, and its signal was coming from under the ground. Stoats drag their prey and cache them underground". All 14 monitored chicks has been killed by early January.
The Kiwi Sanctuary Programme aims to increase the survival of young kiwi in the five sanctuaries so that declining populations begin to recover.
DoC is developing population models that assess the effectiveness of long term kiwi management, and assess the impacts of "kiwi-centric" management on other ecosystem values; and is developing a management prescription for application beyond