It took five years of research after the first specimen was captured when it flew into a fishing boat wheelhouse in 2005, to prove the little bird was a New Zealand storm petrel (Fregetta Maoriana).
Several more birds were soon caught, but in order to show they were New Zealand storm petrels, Dr Robertson's team had to match the birds' DNA to samples taken from a pair of more than 150-year-old New Zealand storm petrel skins on display in Paris.
"We found they were one and the same," Dr Robertson said, "and these birds are a distinct species of storm petrel."
He said it was important to prove they were members of a distinct species, as there had been some concern they could have simply been a different kind of petrel with unusual colouring (known as the "pealea effect").
Conservation work on the New Zealand storm petrel had been held up for several years because its conservation status was listed as "data deficient", meaning more information was required before funds would be released for conservation work, Dr Robertson said, the difficulty being that gathering more information required money.
"It's always a catch-22," Dr Robertson said. "We need the money to find where they breed because it's not going to be an easy effort. They are very small birds, they are nocturnal, and they only come to land at night.
To find where they are, unless you fluke it, takes a bit of effort."
It is not known where the small birds nest, but Dr Robertson said there were suspicions it might be around the Mokohinau Islands, to the northeast of Auckland.
Birdlife International was providing $20,000 for research during the forthcoming season and there was hope the growing body of research would see the species moved out of the "data deficient" category and be treated as a protected species.
"Potentially, taking it out of that and saying 'yes it's a distinct species' should, in my opinion, give it a higher conservation priority," he said.
