Scientists have drawn another curious link between New Zealand's ancient bird species and Madagascar.

Only in recent years did genetic research up-end an uncomfortable theory and reveal that our kiwi was not an Australian immigrant, but, of all things, the closest living relative of Madagascar's extinct, 2.3m-tall elephant bird.

Now, our most mysterious giant bird – the long-lost adzebill – has also been found to have its ancestral roots in the African island.

An international team of scientists, including Canterbury Museum's Dr Paul Schofield and Te Papa's Alan Tennyson, analysed adzebill DNA extracted from fragments of bone and eggshell.

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Comparing adzebill DNA to that of modern bird species led the team to a surprising conclusion: the closest living relative of these extinct New Zealand giants was the tiny Madagascan flufftail, which weighs less than 50g.

Adzebills could weigh up to 19kg.

The just-published findings overturn a previous theory that the adzebill's ancestors were in New Zealand when it was still connected to the supercontinent Gondwana, more than 52 million years ago.

Scofield said the adzebill's ancestors likely flew to New Zealand from Madagascar between 40 and 22 million years ago.

After arriving here, the species grew rapidly, increasing more than 50-fold in mass.

"Adzebills became almost totally wingless but they gained these huge reinforced beaks, which might have been used for digging or to attack prey," Scofield said.

New Zealand had two distinct species of adzebills: the smaller North Island Adzebill and the larger South Island Adzebill.

"The two species likely evolved relatively recently," Scofield said.

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"The separation of the genus into two species probably occurred when the Manawatu Strait separated New Zealand into two islands between 1 and 2 million years ago."

Adzebills died out after early Māori arrived in New Zealand, around the same time as other native giants like the moa and Haast's eagle.

"If they hadn't gone extinct, they would be among the largest living birds," said Alexander Boast of the University of Adelaide, the study's lead author.

Adzebills and kiwi aren't the only New Zealand birds with relatives in Madagascar: the Madagascan teal has shared ancestry with New Zealand teal species.

The adzebill's ancestors likely flew to New Zealand from Madagascar between 40 and 22 million years ago. Photo / Canterbury Museum
The adzebill's ancestors likely flew to New Zealand from Madagascar between 40 and 22 million years ago. Photo / Canterbury Museum

Dr Kieren Mitchell, also from the University of Adelaide, said the ancestors of these birds might have arrived in New Zealand via Antarctica.

"Some coastal regions of Antarctica remained forested and ice free until as recently as 30 million years ago."

ICONS REDEFINED
Moa: A landmark DNA study in 2014 revealed how the moa was more closely related to South America's tinamous than its old bushmate, the kiwi, and concluded both moa and kiwi separately evolved to become flightless after their ancestors flew here.

Kiwi: The same year, scientists corrected an uncomfortable theory that the kiwi's ancestor was an Australian immigrant, and set the record straight with findings linking the icon's lineage back to the extinct, 2.3m tall elephant bird, a native of Madagascar.

Haast's eagle and Eyles' harrier: Another study published this week found both of New Zealand's extinct giant raptors were once related to much smaller, open land adapted Australian relatives. The Eyles' harrier and Haast's eagle diverged from their Aussie relatives about two million years ago — around the same time climate and environmental changes opened up new habitats in the once densely forested islands of New Zealand.

Little blue penguins: In other recent findings, researchers revealed an Otago population of the world's smallest - and possibly cutest - penguin species actually hailed from across the Tasman and had arrived as recently as the past few hundred years.