Operation Rescue

Two tiny kiwi chicks rescued by the Department of Conservation from Okarito have successfully made the 500km trip from the West Coast to a temporary island haven in the Marlborough Sounds

The chicks are the remnant of this year’s newborn in the Okarito Kiwi Sanctuary after a plague of stoats and rats erupted there this breeding season as a consequence of an unusually heavy rimu fruiting.

West Coast Conservator Mike Slater said the sanctuary’s 250 adult population, part of the Bank of New Zealand Kiwi Recovery efforts, were not affected by the stoats although it was unlikely that any newborn chicks, other than the rescued pair, had survived this breeding season. The adult population includes an estimated 100 breeding pairs.

Mr Slater said all 14 monitored newborn chicks died this season - 13 of them are known to have been killed by stoats.

He said DOC rangers went to extraordinary lengths to rescue the two chicks

“One of the major problems was the remaining nests were fortresses deep in the ground or in hollow logs deep in the Okarito Forest which unfortunately prevented any opportunity to simply rescue eggs for incubation in captivity.

“Our staff had to stake out these nests by remaining absolutely motionless for hours on end waiting for a chick to appear at the entrance.

“It is a fantastic tribute to their skill and determination that we managed to rescue two chicks against such odds, especially considering that a freshly trapped stoat was caught next to one of the rescued chick’s nest,” Mr Slater said.

“There is every reason to be optimistic considering that last year’s stoat trapping programme in the sanctuary produced enough chicks to bring us close to the population recovery targets at Okarito, and trapping is working well elsewhere in the country,” Mr Slater said.

“Our problem this year was triggered by an exceptionally good year for rimu fruit which boosted rodent and stoat numbers until they overwhelmed the trapping programme,” Mr Slater said.

“Rimu fruiting of this magnitude is thought to be a 20-year occurrence, so I’m hopeful that we won’t need to mount chick rescue operations like this one in Okarito too frequently,” Mr Slater said.

Representatives from Te Atiawa blessed the chicks prior to their release on Motuara Island.

DOC staff will remain on the island for two days to monitor the chick’s acclimatisation to their new home.

The chicks will return to Okarito after a year on the predator-free island by which time they will have passed 1kg in weight which is big enough to fight off stoats.

ENDS

DOC kiwi information: Paul Jansen 04 471-3236 or 025 410-026 DOC West Coast media liaison: Ian Gill 025 241-6528 Bank of New Zealand Kiwi Recovery Trust: Kieron Goodwin, ph: 09-375-1084 or 029-478-4610

The Bank of New Zealand Kiwi Recovery Trust is a partnership between the Bank of New Zealand and the Department of Conservation established in 2002 and building on an 11-year sponsorship relationship.

www.kiwirecovery.org.nz

Background Information about Okarito kiwi:

Rowi (Okarito Brown Kiwi) are New Zealand’s rarest kiwi, with an estimated 250 surviving in just 10,000 hectares in South Okarito Forest, in South Westland.

It was only in 1994 that they were found to be an entirely new species and given the name Rowi.

Rowi vary from other types of kiwi in a range of ways. The most obvious difference is that rowi are quite greyish in colour and often have patches of white feathers on their faces. They also feel soft to touch, whereas North Island Brown Kiwi feels quite coarse. Both the male and female rowi take it in turns to look after the eggs, while in most other kiwi varieties only the male does this. Rowi can also be quite aggressive.

DOC began investigating the status of the Okarito population in the early 1990’s by surveying Okarito Forest and monitoring breeding burrows. It soon became apparent that the population was in decline and the likely cause of the decline was stoat predation. Stoats were bought to New Zealand to help in the control of rabbits but unfortunately they found that our native birds were an easier target. Although adult kiwi are strong enough to defend themselves, kiwi chicks are extremely vulnerable until they attain approximately 1 kilogram in weight. To date no rowi are known to have been predated by stoats once over this weight. The kiwi recovery programme was instigated and a programme called Operation Nest Egg was set up to remove eggs and chicks to the safety of a predator-free island. Under this programme Rowi chicks spent a year on Motuara Island growing to a juvenile weight of 1kg and then they were returned to the Okarito Kiwi Sanctuary. For the last nine years sponsorship from the Bank of New Zealand has played a key role in the survival of the Rowi population, initially through the Kiwi Recovery Programme, and lately through the Bank of New Zealand Kiwi Recovery Trust. Thanks to Operation Nest Egg 44 juvenile rowi were released into the sanctuary over eight years. Three pairs of these birds are now breeding.

However, while this transfer process is effective in protecting individual chicks, other chicks that hatched and remained in the wild with their parents were still highly vulnerable to stoat attack. To reduce the impact of stoats on wild rowi, in early 2001 an extensive network of stoat traps was set up throughout South Okarito Forest and surrounding areas. The traps are put in wooden trap boxes that keep out native birds. The tunnels are baited with a hen’s egg or pieces of rabbit meat. Never before has stoat control been attempted on such a large scale. Around 1500 traps have been established over the entire 10,000 hectares of the forest. The project is based on a similar but smaller project in the Northern Ureweras which successfully protected kiwi chicks there.

Possums are another threat to rowi. They have been videotaped entering kiwi burrows and may damage eggs and possibly disrupt kiwi breeding attempts. Possum numbers have been reduced to low levels since a major control operation in 1998 and their density is monitored bi-annually.

During 2001-2002, the first rowi breeding season with stoat trapping in place, all chicks were left in the forest. Controlling stoats enabled 30% of monitored chicks to survive. Normally in an unprotected forest the survival rate is probably less than 5%. Unfortunately during the second breeding season in 2002/03 a heavy rimu seeding caused a rat plague which in turn caused a subsequent explosion in the stoat population. The stoat numbers were such that the trapping programme was unable to cope with the influx to the extent that all of the monitored chicks were lost by early January. In response to this tragedy, the Department has temporarily re-instigated the transfer of all of the rest of the season’s rowi chicks to Motuara Island.

NB: Rimu has seasonal highly variable fruiting and a heavy fruiting is called a “mast”. The 2001-2002 rimu mast was regarded as a 1 in 20 year event and was the heaviest fruit production that has been recorded in this area.

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