FROM ITS DRAB exterior, the Native Fauna Centre at Auckland Zoo could easily be mistaken for one of the maintenance buildings alongside it. Inaccessible to the public—a strenuously steep hill sees to that—the centre does not advertise the role it plays in ensuring the future of some of New Zealand’s most endangered species. I had come here to take a behind-the-scenes look at one particular initiative: Operation Nest Egg, part of Bank of New Zealand Kiwi Recovery.

Operation Nest Egg (ONE) began in 1994 in response to evidence that only five per cent of wild kiwi chicks survive the first six months of their lives. Research indicated that this mortality was due, in the main, to stoat predation. But it was found that while stoats have no trouble killing a chick, they are unable to pick off older, heavier birds. When they reach a kilogram in weight, kiwi are able to defend themselves against stoats. ONE was devised to enable them to reach this “safe weight.”

Department of Conservation kiwi researchers Rogan Colbourne and Hugh Robertson devised the strategy of taking kiwi eggs from the wild, incubating them until they hatched and then keeping the chicks in a predator-free “crèche”—typically an offshore island—until they reached the safe weight. (In all but one kiwi species, chicks fend for themselves from the moment they hatch.) They could then be relocated to the area they came from.

ONE was conceived with the Okarito brown kiwi in mind, but because its population was so low—estimated to be around 150 in the early 1990s—it was decided to trial ONE on the more common North Island brown.

To learn the details of kiwi egg incubation, Colbourne built an electronic egg containing temp-erature and motion sensors. Trials using this dummy egg in wild nests confirmed that kiwi, like most other birds, turn their eggs regularly. This piece of information alone resulted in improved hatch rates.
In another trial, to check that artificially incubated chicks could forage successfully, 10 kiwi chicks were released onto predator-free Motukawanui Island, in the Cavalli group. The chicks thrived, reaching the safe weight in around three months. A further trial, involving relocation of the juveniles from the crèche to their original collection area, was also successful.

All the indications were that ONE could help ailing kiwi populations, so four institutions—Auckland Zoo, Rotorua’s Rainbow Springs, the Whangarei Bird Rescue Centre and Napier’s Westshore Nocturnal House—were given the go-ahead to set up breeding units.

Todd Jenkinson, a member of Auckland Zoo’s Native Fauna Team, leads me into the centre’s incubation room. On the walls are charts and diagrams detailing kiwi gestation. A large poster shows all the developmental stages, from early embryo to hatchling.

On a bench are four large incubators, each containing a kiwi egg. The incubators are kept at a temperature of 35º C and a relative humidity of 55 per cent. The eggs are turned four times a day and removed from the incubators for an hour a day to cool down. These actions mimic natural rhythms in a wild kiwi burrow, such as the brooding adult going off to feed.