A release of rowi kiwi on the West Coast on Saturday brings to 200 the number of rowi successfully reared as part of a 15-year breeding programme.
The rowi, also known as the Okarito brown kiwi, is the most endangered species of kiwi.
The Department of Conservation says the population has doubled since 1998, when the breeding programme began.
The juvenile birds being released on Saturday have spent the past 11 months on Motuara Island in the Marlborough Sounds, which has no predators.
They will be returned to their natural habitat at the Okarito kiwi sanctuary near Franz Josef.