RESEARCH linking New Zealand’s diminutive kiwi with a giant extinct bird from Africa is prompting scientists to rethink how flightless birds evolved.
A new report published in the journal Science says DNA-testing indicates the chicken-size kiwi’s closest relative is the elephant bird from Madagascar, which grew up to three metres tall and weighed up to 250 kilogrammes. It became extinct about 1,000 years ago.
The authors say the results contradict theories that the kiwi and other flightless birds, including the ostrich and emu, evolved as the world’s continents drifted apart 130 million years ago.
Instead, they say, it is more likely their chicken-size, flight-capable ancestors enjoyed a window of evolutionary ascendancy about 60 million years ago, after dinosaurs died out and before mammals grew big.
Those birds, the authors say, were likely to have flown between the continents, with some staying and becoming the large, flightless species we know today.
Alan Cooper, a professor at the University of Adelaide in South Australia and a co-author of the paper, said the DNA results came as a huge surprise given the differences in size and location between the kiwi and elephant bird.
“This has been an evolutionary mystery for 150 years. Most things have been suggested but never this,” he said. “The birds are about as different as you can get in terms of geography, morphology and ecology.”
Prof Cooper, a New Zealander by birth, is hoping the paper will also bring him a measure of redemption.
Two decades ago, he and other scientists discovered genetic links between the kiwi and two Australian flightless birds, the cassowary and the emu.
That led to New Zealanders believing their iconic bird might have come from Australia, their traditional rival.
“There was a huge outpouring of angst,” Prof Cooper said. “New Zealanders weren’t tooimpressed.”
The nation’s identity is so entwined with the bird that New Zealanders call themselves kiwis and have also given the name to their currency and the kiwi fruit.
However, it turns out that if the emu was a cousin to the kiwi, the elephant bird was a sibling.
Prof Cooper said it had taken until now for DNA techniques to advance enough to get a usable result from the ancient bones of the Madagascan bird.
He said the bird took its name from Arabic legends that suggested it was so fearsome it could grab an elephant.
There is little basis for the legend, given the bird was a herbivore.
In fact, it was probably humans that hunted it into oblivion, Prof Cooper said.
Trevor Worthy, a research fellow at Australia’s Flinders University and a paper co-author, said it was likely the kiwi stayed small and took to eating insects at night because it did not want to compete for habitat and food with another New Zealand flightless bird, the moa, which is also now extinct.
He added that it was strange the kiwi and elephant bird were such close relatives. “One got big, one stayed little,” he said.
Massey University professor David Penny, who peer reviewed the study for Science, said the results were very interesting and helped complete the puzzle of flightless birds.