New Zealand is home to two species of type of bird known as rails: the Pukeko and Takahē . They may look very similar, and it would be tempting to think that are closely related, but that is not the case.
Pukeko are not indigenous to New Zealand, but occur across many South Pacific islands and in Australia, southern Asia, Africa, parts of Europe (Spain and Portugal, for instance), Central America and Florida. Outside of New Zealand, the birds are usually referred to as purple swamphens. They are classified as a single species, Porphyrio porphyrio, with six subspecies. The swamphens which colonized New Zealand probably flew across from Australia a thousand years ago or less, and share the subspecies name Melanotus along with swamphens in the Kermadec Islands, Tasmania, eastern and northern Australia and the South Pacific. Despite their belonging to the same subspecies, New Zealand swamphens are slightly larger than their Australian neighbours. They are very common and not threatened.
The Takahē’s ancestors, on the other hand, are endemic to NZ and apparently from Africa arriving in New Zealand many tens of thousands of years ago before NZ parted company from Australia and the rest of Gondwanaland. They are apparently now found only in NZ.
As such, those birds stranded in NZ developed their own traits based on the specific threats and environments they were faced with. Their predators weren’t on the ground, as there were no mammals or marsupials to hunt them: they were in the sky. It was a time when the huge, native Haast’s Eagle (the largest that ever lived) would have hunted the Takahē from above.
In the absence of any such terrestrial threats, the descendants of these birds became flightless, long-lived and slow breeders. The ancestors of Takahē lost the ability to fly since it is energy intensive and they had no need for it. With their dark blue and green feathers, they blended into the vegetation, hiding from anything that could be scouting from the skies. They became larger, and are now the world’s biggest rail with an average weight of 2.7kg (6lbs). As such they were prey for human consumption and for the various predators that we brought with us with the first arrivals of Māori settlement around 1200CE.
While Pukeko are common around NZ, the Takahe are generally limited to South Island's Fiordland and within that the flat glacial valley wetlands. The birds almost became extinct, but after strenuous efforts there are about 500 left.
The are an interesting example of how nature has evolved two different species from diverse origins to a common form to enable survival under the same conditions.
