Project Island Song co-ordinator Richard Robbins said it was the most challenging re-introduction to date because kakariki, unlike other species returned so far, could fly off the island.
Various techniques had been used to "anchor" the birds to the island, including setting up a feeding station and releasing then in a valley with no view to the mainland or other islands.
It seemed to have worked because trail cams, or motion-activated cameras, had recorded 33 of the 40 birds at the feeding station in recent weeks. Individual birds could be identified by their leg bands.
"We were a bit concerned because this was the first species that could actually fly off the islands. That's better than we expected," Mr Robbins said.
The other seven could still be on the island but avoiding the feeding station.
There was plenty of food on the island but volunteers were continuing to replenish the feeding station, at irregular intervals so the birds didn't become dependent, to keep them in the area.
Kakariki normally laid their eggs in late October to early November with fledglings emerging from the nests about a month later.
Trail cam footage showed some birds had paired up so the signs were good, Mr Robbins said.
Breeding confirmation would come from sightings of unbanded kakariki, with a lack of leg bands showing the birds had been hatched on the islands.
Kakariki nested in hollows and crevices anywhere from the treetops to the base of flax plants, making them vulnerable to introduced predators. Possums never reached the Ipipiri islands but rats and mice were prolific until poison drops and trapping wiped them out in 2009.
Project Island is a joint initiative by community group Guardians of the Bay of Islands, the Department of Conservation, Rawhiti hapu and island landowners.
