Australian and New Zealand scientists say fossil evidence suggests the nocturnal kiwi likely evolved from a tiny bird that could have flown from Australia across the Tasman Sea to New Zealand.
The study results were supported by genetic evidence the kiwi was related to the Australian emu and not the New Zealand moa, an enormous emu-like bird that became extinct about 700 years ago, Trevor Worthy of Australia's Flinders University said in a statement reported by China's Xinhua News Agency Tuesday.
"One of the distinguishing attributes of the kiwi is that it lays an enormous egg, which is about a quarter of the bird's body weight and occupies most of the bird," said Worthy, an expert on the moa.
The Kiwi's egg size had led some experts to theorize the kiwi was highly derived from a large moa-like ancestor, but a fossil from New Zealand's South Island contradicts that theory, the researchers said.
"This fossil from the early Miocene, about 20 million years ago, shows us that it's a tiny bird about one third of the size of a small kiwi today," Paul Scofield of New Zealand's Canterbury Museum said. "It suggests the opposite is, in fact, the case that the kiwi has developed towards a larger size, a trend that is seen in many birds from the early Miocene."
"And if, as the DNA suggests, the kiwi is related to the emu, then both shared a common ancestor that could fly," he said. "It means they were little and had wings, and that they flew to New Zealand."