The 11,400-hectare sanctuary is home for at least 85 per cent of the known distribution of the rare Haast Tokoeka variety of kiwi, ranked by the Department of Conservation as 'nationally critical'. The remaining known Haast Tokoeka are spread up the Arawhata and Waiatoto rivers and around the Selbourne Range. The sanctuary population is estimated to be about 200 individuals.
The sanctuary rises from sea-level to 1300-metres, with the upper alpine area frequently covered in snow. Higher reaches of the sanctuary are dissected by major earthquake faults, hazardous barriers to both birds and Department of Conservation staff.
The Haast Tokoeka population has been declining because of stoats, which kill young chicks less than 1000-grams in weight. Research shows that recruitment of new birds to the population is low because pairs lay few eggs (one or fewer each year), and many chicks and juvenile birds die.
The Department of Conservation is carrying out intensive stoat control inside the sanctuary, monitoring results closely to ensure the variety survives.
Monitoring during the 2005/06 breeding season showed only 19 per cent of monitored chicks survived to 1000 grams, a weight at which they are safer from stoat predation. Population modeling has shown that 40 per cent survival is needed to sustain the population.
Of the four kiwi chicks that survived, all were part of Operation Nest Egg. One hatched in the sanctuary and the other three were removed as eggs – one of them after it was abandoned by the adult kiwi.
Operation Nest Egg
The Operation Nest Egg programme was first trialed at Haast during the 2003/04 breeding season, to boost the number of juvenile kiwi.
A small percentage of Haast Tokoeka eggs are taken from the nest and artificially incubated until they hatch. The chicks are then moved to a predator-free sanctuary in Southland until they reach the magic 1000-gram weight. It is hoped the programme will help bring back the nationally critical Haast Tokoeka back from the brink of just 300-odd birds.
As a result of Operation Nest Egg, three juveniles born in the 2003/04 season live in the sanctuary, and in April 2006 they were joined by the four chicks from 2005/06 season.
Eleven other kiwi juveniles that were hatched and raised within the sanctuary are also monitored.
Future Management of Haast Tokoeka
Just as for Rowi, researchers believe the best way to boost the slow-growing population of Haast Tokoeka is to stimulate the birds to produce more eggs, and to ensure more chicks survive. While both can be achieved through Operation Nest Egg in the short-term, the aim is to discover ways to achieve this in the wild so that the Haast Tokoeka’s long-term future can be more assured.
Some birds will be transferred to high fertility pest-free islands to see if more eggs are laid. Also, rats and possums will be controlled within the sanctuary, along with stoats, to reduce competition for the Rowi’s insect food. It is hoped better fed birds will produce more eggs.
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