The Department of Conservation says diving petrel are still under threat, despite an increase in breeding numbers
Conservationists are celebrating a bumper breeding season for the critically endangered bird - found only on Whenua Hou / Codfish Island, near Rakiura / Stewart Island.
There are now 210 of the birds, up 5 percent on previous years.
DOC technical advisor seabirds Johannes Fischer told Morning Report it was good news.
"The species has been flatlining for the last six years, so an increase is very welcome."
He could not say what the reason for the increase was, but he put it down to "population fluctuation" among the species.
Fischer described the bird as "a penguin that can fly with blue feet, that's in the palm of your hands".
"From an ecological perspective, it is the only seabird species in Aotearoa New Zealand that only breeds in sand dunes."
However, he said the island was predator-free but other threats to the birds remained including rising sea levels which were damaging the dunes they bred in..
DOC has been monitoring the population for seven years.