So far four bird species have been returned to the islands but Duvaucel's gecko will be the first reptile, a milestone for the project which started in 2009.
Project Island Song co-ordinator Richard Robbins said the geckos — ideally 34 female and 14 males — would be caught on Mauimua in the Hen and Chicken Islands off Bream Bay, which had a population estimated at 1000-plus.
The geckos were nocturnal so could be caught by night as they searched for food or by day as they sought out hiding places.
The seven-strong catching team cleared biosecurity checks on Thursday but poor weather meant their departure from Whangarei had to be delayed until yesterday morning. The boat would have to make a beach landing so can't leave in a big swell.
The team comprised members of the Guardians of the Bay and Te Rawhiti hapu Ngati Kuta and Patukeha, along with NorthTec reptile expert Ben Barr.
Their first job was likely to be removing geckos from the island's ''very cosy'' hut, Mr Robbins said. However, the team would try to catch geckos all over the 140ha island to ensure genetic diversity.
They planned to return to Whangarei on Sunday with the geckos in specially designed transport tubes. They would then be transported by vehicle to Rawhiti for a powhiri, then taken by boat to the islands early Monday morning.
Mr Robbins said most of the females should be pregnant so would give birth to two live young soon after the release.
''It's very exciting. It's a new phase for us.''
Other reptiles would follow but the species had yet to be decided. A few skinks and geckos had managed to hang on when the islands were farmed and over-run by rats and mice and were now starting to re-emerge.
He was confident there were no Duvaucel's geckos on the islands because they were so big they would have been noticed by now. It was probably 100 years since Duvaucel's gecko was last in the Bay of Islands, he said.
The geckos eat invertebrates, nectar and fruit. Their relatively slow breeding makes them vulnerable to pests.
