Research into the kiwi’s DNA shows their closest relative is the now extinct giant elephant bird from Madagascar (Mullerornis agilis).
They are also more closely related to Australia’s emus and cassowaries than New Zealand’s other well-known ratite, the moa.
Madagascar is a long 11,200 kilometres away for a bird that can’t fly, while Australia is about 4000 kilometres as the kiwi walks.
So, just how did the kiwi journey to New Zealand? Three very different theories have been put forward to explain the mystery.
An ancient ancestor
Some suggest the kiwi’s ancestor was already around when New Zealand broke away from Antarctica and Australia 60 million years ago.
If true, it removes the question of whether or not the kiwi could ever fly. It would also mean our national icon originated around the same time as the dinosaurs.
Walking to New Zealand
Islands rise up and submerge as tectonic plates move. A string of islands have come and gone between New Caledonia and Northland during the past 50 million years. It is possible that the kiwi and other species moved from one island to the next as they rose and fell – using them like stepping-stones to reach New Zealand.
A flying kiwi
Once considered the least likely explanation, a flying kiwi seems more possible following DNA analysis linking kiwi with Madagascar’s extinct elephant bird. The findings make little sense if their common ancestor could not fly – how else could kiwi have got to New Zealand?
Scientists estimate the common ancestor lived 50 million years ago, a partridge-like bird that flew between landmasses in search of new homes.
The hypothesis challenges the long-held view that all ratites had a flightliess ancestor. Of ratites alive today, only the South American tinamous can fly – and not very well – making it the exception, not the rule.
Another argument against a once-flying kiwi is the theory that its ancestor was much bigger than today’s bird. The kiwi egg is so huge it should theoretically be laid by a bird two or three times bigger – closer to a cassowary in size. And that would have been much too big to fly across the Tasman Sea, even millions of years ago when the gap was narrower.
The mystery of the kiwi’s arrival remains subject to debate.