The mysterious demises of two of New Zealand's most enigmatic native birds have been explored in a new DNA investigation reaching back far into the past.

And now scientists are reasonably sure that what tipped the South Island kōkako and huia into oblivion wasn't issues within their own population, like genetic problems, but the same thing threatening what we have left – habitat loss and pest predators.

The lead author of a new study into the two species, Dr Nicolas Dussex, of the University of Otago and Swedish Museum of Natural History, said his colleagues wanted to learn what drove the loss of the birds.

Very little was known about the South Island kōkako and huia, forest songbirds Dussex described as "iconic and somehow mysterious", and which were last seen in 1960s and 1907 respectively, but recent advances in the extraction and analysis of ancient DNA provided the opportunity scientists needed to find out more.

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The study, just published in Biology Letters, produced what Dussex called "very surprising" results.

The researchers mapped the birds' complete genomes and saw a response to ice-age climate change many thousands of years ago, but no signs of genetic problems common in small populations such as inbreeding.

This suggested a rapid population decline possibly caused by habitat loss and new predators introduced by the Europeans.

"Because even the earliest Polynesian settlers more than 700 years ago had a significant impact on forest cover, we would have expected huia and South Island kōkako populations to have survived at small population sizes for centuries and thus to have experienced an increase in inbreeding," he said.

"However, our data did not show evidence for inbreeding and indicated that the two species still had quite a bit of genetic diversity close to the time of extinction.

"This means that their extinction was most likely not driven by genetic effects and inbreeding, but that further habitat loss and introduction of mammalian predators by European must have triggered a rapid extinction."

Dussex says this is the first study to generate high-quality genomes from historical specimens of extinct New Zealand species.

"Using complete genomes allowed us to reconstruct the birds' population history, and, more importantly, to determine whether genetic effects could have contributed to their extinction.

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"While we focused here on two extinct species, understanding the role of genetic effects in the extinction process is extremely relevant to the study of declining and inbred populations, such as the kākāpō, saddleback and kiwi.

This knowledge can thus contribute the conservation and recovery of endangered species potentially exposed to negative genetic effects."

Co-author Dr Michael Knapp, of Otago's Department of Anatomy, said the team hopes its work will stimulate similar research in other extinct or endangered endemic species from New Zealand.

The South Island kokako. Image / Paul Martinson / Te Papa
The South Island kokako. Image / Paul Martinson / Te Papa

"Recent advances in ancient DNA mean that it is the right time to study extinction from a genomics perspective.

"So far, very little is known about the role genetic effects play in the process of extinction.

"This research is thus very timely and extremely relevant to the understanding of the decline in biodiversity in New Zealand."

New Zealand currently has 23 species at risk of immediate extinction, including the orange-fronted parakeet (Kākāriki), Chatham Island black robin, New Zealand fairy tern and the white heron.

A number of rare birds are also being threatened by the heavy seeding of the country's beech forests this year, the largest in 45 years.

Forest & Bird has warned that this will result in a huge increase in introduced predators, such as rats and stoats, by spring.

However, a recent survey of 510 people has revealed that only 19 per cent of Kiwis believe that the country's rare birdlife is in immediate crisis, with more than 40 per cent thinking that they are doing well. Seventy-seven per cent are completely unaware of the mass seeding event.

After hearing the statistics, 80 per cent felt sad and upset, and 44 per cent reported feeling angry.

More than 50 per cent said that they wanted to do something to help.

Kiwi winery Toi Toi is currently working with Forest & Bird on a fundraising campaign, in which a donation will be made from every bottle sold until September 30.