A project to restore dwindling kaka numbers in the Abel Tasman National Park is one of the area's most significant conservation projects to date, says a local ornithologist.
Peter Gaze said four of the female forest-dwelling parrots were to be released today in a bid to boost what was currently thought to be an all-male population in the park.
Project Janszoon, a privately funded trust which focused on ecology restoration in the Abel Tasman, was working with the Department of Conservation on the kaka project.
"Project Janszoon was working on a range of restoration projects and bird life in the Abel Tasman, but I'm predicting this kaka restoration will be the most significant," Mr Gaze said.
Trust spokesperson Robyn Janes said it was the first time kaka had been relocated into the national park.
The birds bred in the lower South Island would be released from an aviary set up in the area, where they had been acclimatising for the past month.
"We have worked long and hard to find birds to bring to the park, as there has been much discussion about whether North Island kaka - there are plenty available in Wellington from Zealandia - can be brought to the South Island.
"The experts decided they must come from the south, so these four have been bred in Te Anau, Invercargill, and Dunedin," Ms Janes said.
Mr Gaze was contracted by the trust to advise on wildlife management.
In the 1800s, huge flocks of kaka thrived on the flowering rata in the area that eventually became the Abel Tasman National Park, he said.
But the population had been devastated by predators targeting chicks and nesting females, and while restoration would take time, they were confident results would be "spectacular".
"Stoats prey on eggs and chicks, and kill nesting females.
"They've been in decline across the South Island, but Project Janszoon has a commitment to long-term pest control which we know allows kaka to thrive," Mr Gaze said.
They were "long-lived" birds, and the aim was to correct gender imbalance and bring more into the park over the next five to 10 years, he said.
Work is also underway to radio-monitor kaka in the Nelson Lakes National Park to locate eggs or chicks to be hatched at Nelson's Natureland zoo to be used in a breeding programme.