"We're ecstatic. They're the first tieke to breed on the island in more than 100 years, and they're the northernmost population in New Zealand."
Mr Robbins said the wet summer meant there was plenty of food for the birds, helping to ensure a good breeding season.
Tieke liked to eat small invertebrates but would also feed on nectar and berries.
The group had yet to carry out a bird count - that would take place later this month - but there had been plenty of sightings and people were hearing the tieke's distinctive call all over Urupukapuka.
"Project Island Song is starting to live up to its name," he said.
A few tieke families had taken up residence at Otehei Bay, where the ferries call in and where they were easy to spot.
Czech-born Darina Cincurova, now living in Russell, said it was a privilege to be one of the first people to get a photo of a tieke fledgling on Urupukapuka.
"They were beautiful. Everywhere you looked they were jumping from branch to branch. I didn't expect that at all," she said.
Also enjoying a good season were 40 popokotea (whiteheads) released last year on Motuarohia Island. Mr Robbins said the small, fast-moving birds were harder to keep track of but sightings of unbanded fledglings proved they had been breeding.
He cautioned that it would be five years before the group would be certain that the re-introductions had been successful. Once the population was in the hundreds he would be confident they could survive a dry summer and avoid inbreeding.
Project Island Song is a joint initiative by community group Guardians of the Bay of Islands, the Department of Conservation, private landowners, and Rawhiti hapu Patukeha and Ngati Kuta.
Next month the group plans to release 80 popokotea on Moturua and Urupukapuka islands, followed by a release of 40 toutouwai (North Island robins) on Urupukapuka in May.
The popokotea will come from Tiritiri Matangi Island in the Hauraki Gulf and the toutouwai from Pureora Forest in the King Country. The translocations are funded by the Air New Zealand Environment Trust and Lottery Grants Board.
In the 1960s, the total population of North Island saddlebacks dropped to just 500, all of them on Taranga Island off Bream Bay. There are now thought to be at least 5000 at various islands and sanctuaries around the country.