A study of the Cook's petrel seabird has found that the country's two colonies migrate to different parts of the world and do not interbreed.
Scientists at the National Institute of Water and Atmospheric Research (NIWA) and Auckland University arrived at their conclusion after testing the DNA from birds killed more than 100 years ago.
The scientists tracked both New Zealand's colonies of Cook's petrel - a bird about the size of a pigeon that migrates around the Pacific.
They found that birds from Little Barrier Island in the Hauraki Gulf head to the North Pacific while those that breed on Codfish Island, close to Stewart Island, prefer the waters off South America.
The two genetically distinct groups don't mix and their breeding cycles are about a month apart.
The scientists used tiny 2 gram microchips to track the birds and relied on DNA from museums in the United States to corroborate their findings.
