Australasian Science: Australia's authority on science since 1938

Flight of the Kiwi

What came first: the kiwi or its enormous egg? Credit: Rod Morris Photography

What came first: the kiwi or its enormous egg? Credit: Rod Morris Photography (http://www.rodmorris.co.nz)

By Michael Lee & Trevor Worthy

How did large flightless birds such as emus, ostriches and kiwis disperse around the globe? Surprisingly, it seems they flew everywhere.

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The presence of large flightless birds across all of the southern continents has been one of the enduring mysteries of evolution. The emu and cassowary (Australia), kiwi and extinct moa (New Zealand), rhea (South America) and ostrich (Africa) form a close-knit group of birds called “ratites”.

Scientists have long wondered how these landlubbing avians managed to disperse across landmasses separated by large swathes of water. A plausible answer proposed a few decades ago has now been overturned by Australasian scientists, with accumulating evidence supporting a more outlandish and exciting scenario. This new research also resolves the long-standing question of what came first: the kiwi or its gigantic egg?

Deep time and continental drift have been integral to a rather prosaic explanation for the current wide distribution of ratites. It was proposed that ratites were an extremely old group that roamed across the ancient southern supercontinent Gondwana. When Gondwana started breaking up, every major continental fragment that split away contained some ratites, which gradually evolved into distinctive new endemic forms while being “rafted” in slow motion via continental drift.

This idea, pioneered by leading ornithologist and biogeographer Joel Cracraft, was intuitively satisfying and initially had some support from evolutionary trees. The ostrich was...

The full text of this article can be purchased from Informit.