For the first time in possibly 100 years, the greyfaced petrel has returned to nest on the steep cliffs of Whangarei Heads.
A burrow was discovered a month ago by Bream Head Conservation Trust project manager Adam Willets as he hung over a cliff edge during the routine check of a site.
Mr Willets said he instantly recognised it as a petrel's burrow - helped by the strong ammoniac smell seabirds leave in their nests. Further surveillance using an infrared camera revealed other petrels.
At least one of eight known birds is now sitting on an egg.
"It's very cool,' Mr Willets said of the first naturally repatriated colony of the species at Bream Head.
Predation by invasive killers, including humans, meant the birds had not nested on the mainland for up to 100 years.
The discovery was all the more exciting because none of the birds appeared to be tagged, indicating they were not from an existing breeding programme. When the as-yet unhatched chicks fledge they will be tagged, Mr Willets said.
In Bream Bay, greyfaced petrels have been confined to islands such as Taranga, of the "hen and chicks" group, and Matakohe/Limestone Island, where a colony was established in a Department of Conservation (DOC)-controlled translocation and breeding programme.
Mr Willets said the new colony would probably thrive because of the success of the Bream Head trust's predator control and other biodiversity protection programmes.
Trust chairman Greg Innes said there was exciting potential for ongoing transformation at Bream Head.
"That the petrels feel safe to return to Bream Head to raise young is a victory for all those who have worked so hard to manage the reserve's comprehensive ecosystem and rid it of predators over the past 13 years," Mr Innes said.
Bream Head was on the road to becoming one of the finest natural ecosystems in the country, providing a home for many species of native New Zealand wildlife not seen on the Northland mainland for many generations, he said.
The trust recently completed its community-developed Five Year Plan and last year received three year's funding of $160,000 from DOC's Community Conservation Partnerships Fund for a programme to reintroduce other native wildlife.