Five years after the relationship between New Zealand’s kiwi and the extinct Madagascan elephant birds was revealed, new research suggests that New Zealand’s giant, flightless – and now extinct – adzebill also had African origins.
Among the bird’s closest living relatives are the pint-sized flufftails in the genus Sarothrura from Africa, and the relationship “strongly suggests that the ancestors of the adzebills flew to New Zealand after it became physically isolated from other land”, say researchers led by Alexander Boast from the University of Adelaide in Australia.
It’s a relationship you wouldn’t pick at first sight, it must be said. Adzebills grew to as much as 19 kilograms, while flufftails can weigh as little as 25 grams.
Like the better-known moa, the two species of adzebill – the North Island adzebill (Aptornis otidiformis) and South Island adzebill (Aptornis defossor) – disappeared after the arrival in New Zealand of the Maori people, who hunted them and cleared their forest habitats. Unlike the herbivore moa, adzebills were predators.
“The adzebill were almost completely wingless and had an enormous reinforced skull and beak, almost like an axe, which is where they got their English name,” says Boast.
“If they hadn’t gone extinct, they would be among the largest living birds.”
Boast worked with researchers from Australia, New Zealand and the US to analyse genetic data from the two adzebill species.
“A lot of past genetic research and publicity has focused on the moa, which we know were distant relatives of the ostrich, emu, and cassowary,” says co-author Kieren Mitchell.
“But no-one had analysed the genetics of the adzebill, despite a lot of debate about exactly what they were and where they came from.”
Mitchell says it’s possible that ancient migration of birds between Madagascar and New Zealand occurred via Antarctica.
And according to Paul Scofield from New Zealand’s Canterbury Museum, the North Island adzebill likely evolved from its South Island counterpart relatively recently.
“We know the North and South Islands were joined by a narrow piece of land around two million years ago. Adzebills probably developed in the South Island, then walked over this land bridge to the North Island,” he says.