The rare New Zealand storm petrel, thought to be extinct until 2003, appears to be breeding in the Hauraki Gulf, reinforcing the claim it is endemic to New Zealand.
A research team captured five of the 35 gram birds on Wednesday with specifically-designed net guns and found four of them had bare brood patches on their belly, which are used to incubate eggs.
This suggested they were breeding locally, probably on islands within the Hauraki Gulf Marine Park, Department of Conservation seabird expert Graeme Taylor says.
"It's wonderful to think that these birds are breeding right now on islands in the outer Hauraki Gulf, quite possibly in sight of where the researchers captured them," Hauraki Gulf Forum chairman John Tregidga said.
The discovery gives New Zealand more claim to the birds than if they were visitors that bred elsewhere, the research team says.
The bird was presumed extinct until its rediscovery by bird watchers in the Hauraki Gulf Marine Park in 2003.
Further captures will continue through February and March will be made to help researchers learn more about the petrels, which are listed as critically endangered.
NZN