Kiwi recovery programmes are proving their worth even though the national population of the threatened bird continues to decline, Conservation Department science officer Rogan Colbourne says.
Mr Colbourne has been part of the BNZ Operation Nest Egg scheme. The Hawke’s Bay group released its 100th young North Island brown kiwi into the Kaweka Ranges on Thursday.
Nationally the kiwi population is thought to be falling by about 6 per cent a year, but Mr Colbourne said local programmes were making a difference, in some cases having increased the local population.
“At Okarito [on the West Coast] they have increased the population from 150 to more than 300,” he said.
In Hawke’s Bay, with a kiwi population of fewer than 1000, the addition of 100 young birds since 2003 was significant. Kiwi lived on average to 40 – and even to 60 – if there were no predators.
In these programmes, eggs are taken from the wild and incubated, then the hatchlings are kept in a predator-proof environment till considered big enough to fend for themselves in the wild.
“There is a 90 per cent hatch rate with these eggs, compared with only 50 per cent in the wild, for various reasons,” Mr Colbourne said.
“Possums can eat the eggs, the adults can damage them accidentally, and there can be bacteria after rainfall.
“Once hatched [in captivity] about 80 per cent reach the sub-adult stage and once they are released about two-thirds survive in the wild, though that varies from area to area.”
Of kiwi hatched in the wild, only about 5 per cent survived to become adults, as predators such as stoats, ferrets and feral cats ate the young birds. Ferrets and dogs could kill adults, and dogs were a particular worry in Northland.
About 15 recovery groups were operating in the North Island, with assistance from DOC and other organisations, Mr Colbourne said.
The Hawke’s Bay group is led by the Environment, Conservation and Outdoor Education Trust.
Spokesman Alastair Bramley said the survival rate for the kiwi released in Hawke’s Bay was about two-thirds overall, but it had been up at 90 per cent till an outbreak of ferret attacks in 2008.
“We haven’t lost any since then,” he said.
Dogs were not such a big problem in Hawke’s Bay because hunters there had to put their dogs through kiwi aversion training before they could register them, Mr Bramley said.
The 100th kiwi has been named Parauri and was released in the Kawekas after a ceremony at the Pan Pac Kiwi Creche, inland from Tutira.