Ancient DNA Reveals Origins of Flightless Kiwi Bird and How it Spread: It Flew

Scientists have uncovered a little bit more about the origins of New Zealand's flightless bird, the kiwi, by examining its DNA. It turns out that its closest relative is not the emu as was previously thought. Instead, it's most closely related to the extinct Madagascan elephant bird. Not only that, but these birds both once flew.

Scientists have long wondered about the origins of giant flightless "ratite" birds, such as the emu and the ostrich, which are mostly found across the southern continents. This particular group contains some of the world's largest birds, and scientists once thought that the different "ratite" species formed after the flightless birds were isolated by separation of the continents over the past 130 million years.

Yet DNA evidence points to the fact that this isn't the case. The researchers extracted DNA from the bones of two elephant bird specimens from the Museum of New Zealand. They found that there was a close genetic connection with the kiwi, despite striking geographical differences. In addition, the DNA allowed them to estimate when the ratite species had separated from each other.

"This result was about as unexpected as you could get," said Kieren Mitchell, one of the researchers, in a news release. "New Zealand and Madagascar were only ever distantly physically joined via Antarctica and Australia, so this result shows the ratites must have dispersed around the world by flight."

It's very likely that ancient, flying ratite dispersed across the world right after the dinosaurs went extinct and before mammals dramatically increased in size. The ratites took advantage of a small window of opportunity before mammals became the dominant group and became large themselves. Once mammals became the dominant group, though, the birds remained small unless they were on a mammal-free island.

"It also explains why the kiwi remained small," said Trevor Worthy, one of the researchers, in a news release. "By the time it arrived in New Zealand, the large herbivore role was already taken by the moa, forcing the kiwi to stay small, and become insectivorous and nocturnal."

The findings reveal a bit more about how these flightless birds evolved and spread across the globe. It also tells us a bit more about the kiwi and its ancient origins.

The findings are published in the journal Science.