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Conservation officials today formally declared the South Island kokako extinct, saying there had been no confirmed sightings for 40 years.

Rod Hitchmough, a scientific officer at the Department of Conservation (DoC) told a press briefing in Wellington that the kokako decision had attracted controversy.

"But the definition of extinct is that we are absolutely certain the last individual has died," said Mr Hitchmough, who compiled DOC's latest lists of threatened species, including six native insects and snails also declared extinct.

"It was last seen on the South Island in 1967," he said.

There had been further reports on Stewart Island in 1987 and other more recent sightings, but these had not been corroborated.

A panel of bird experts which drew up the previous list of the threat status of native animals and plants in 2002 had not been able to decide with certainty whether it had died out.

"There have been more recent sightings recorded but they have been less well-documented," Mr Hitchmough said.

"Now, given there have been no further convincing records, the panel decided to bite the bullet and list it as extinct.

"But it was probably extinct years ago".

Less than a year ago, veteran searchers seeking signs of the kokako unsuccessfully searched a valley east of Puysegur Point in Fiordland National Park for signs of the grey bird with orange wattles at each side of the beak.

That South Island kokako investigation team included Christchurch researcher Ron Nilsson, who has spent 20 years searching remote valleys in Nelson, Westland, Fiordland and Stewart Island.

Other searches have been made in Granville State Forest in the West Coast's Grey Valley and further north in the Paparoa Range near Charleston.

Conservation Minister Chris Carter told the Wellington briefing that the new threatened species list updated the "threat classification" status of 5819 of New Zealand's native plants and animals, and 44 had been given a change in status.

Almost half of those were listed in one of the seven threatened categories, and the rest required further research to determine if these were threatened or not.

"Some have improved, like the crested grebe and black petrel, others, such as the grey duck and riflemen are more endangered," Mr Carter said. "It's a wake-up call for us, as a country".

"Human-induced threats and the introduction of predators and pests continue to plague our native species," he said.

"The species that make up our country - the unique bird, reptile, plant and insect species that are endemic to these islands of ours - are what helps to make us New Zealanders, give us a unique place in the world and give us our identity," said Mr Carter.

Settlement of New Zealand by Maori and Europeans had made an incredible impact on the nation's biodiversity, Mr Carter said.

The total number of threatened species reported in the new list rose by 416 to 2788 - in many cases because new information had become available since the lists were last reviewed in 2002.

Another 984 species have been listed as "data deficient".

He said the list would be used to prioritise management of threatened species.

The battle to retain biodiversity was not only about resources - for which conservation had to compete with spending on areas such as health and education - but was also dependent on expertise in developing management plans and providing the science for managing threatened species.