When the ancient kiwi first arrived in New Zealand about 30 million years ago, there was probably only one species.

New Zealand's landscape has changed many times since it split from Gondwanaland, 80 million years ago. At various times the three main islands of New Zealand (North Island, South Island and Stewart Island) were joined together, or split in quite different shapes.

For example, during the Oligocene (37 to 23 million years ago), most of New Zealand was covered by a shallow sea, breaking the landmass into a series of small islands.

How Species Develop
As the land changed, groups of kiwi became cut off from other groups. Without flight there were many barriers - mountains, wide rivers and seas, and harsh terrain including glaciers. Isolated groups could breed only amongst themselves, sharing a gene pool.

As generations passed, kiwi in each group became increasingly different from kiwi in other groups.  Nature selected traits most useful to their local environments and the groups became so different they no longer naturally interbred. Eventually they became separate species altogether. How the Kiwi Species Evolved The two new species identified by the genetic DNA analysis in 1995 are very interesting because the break between them is in the middle of the South Island, near Okarito. It suggests that Tokoeka is the primitive kiwi.

What Caused the Split?
Probably it was ice ages and the glaciers they created, some of which ran from the mountains to the Tasman Sea. For small birds that could not fly, these natural barriers through the middle of the South Island would have been formidable.

We think Tokoeka split into two species when the northern South Island group became isolated and evolved into Brown Kiwi. Some of these travelled north and reached the North Island during a time when sea levels were low and the two islands joined by land. There they evolved into Brown Kiwi.

The South Island Brown Kiwi
South of the glacier barriers, a separate species of kiwi evolved – today known as the Tokoeka. This species ended up with two varieties – Haast Tokoeka  and Southern Tokoeka.

One of the things that confused taxonomists for so long is that the Rowi still shows some of the physical and behavioural traits of Tokoeka, including soft plumage and shared incubation.

The map shows how the Brown Kiwi moved and evolved into two species, and the location of Tokoeka.

Not shown are the Great Spotted Kiwi, which has always lived in the north-west of the South Island, and Little Spotted Kiwi, which once occurred throughout New Zealand.