Seven critically endangered shore plover chicks have hatched on pest-free Motutapu island in the Hauraki Gulf.
There are just 245 mature shore plover/tuturuatu, endemic to New Zealand, remaining, including 17 that are resident on Motutapu.
Shore plover were released on pest-free Motutapu in 2012, a year after Motutapu and neighbouring Rangitoto - the two islands are joined by a short bridge - were declared free of introduced predators including rats, stoats and possums that eat eggs and chicks of native birds.
Shore plover were once widespread around the coast of the North and South Islands but have been driven to the brink of extinction by rats and other introduced predators.
By 1990 there were only 130 shore plover. All these birds were on one island, Rangatira Island in the Chatham Islands, which is free of introduced predators.
"Pest-free Rangatira provided a lifeboat, preventing shore plover from becoming extinct," said Dave Houston, who leads the Department of Conservation Shore Plover Specialist Group.
"But Rangatira is basically becoming full. We're now using Motutapu and other pest-free islands to try and secure the survival of this species."
In the early 1990s, DoC took shore plover eggs from Rangatira and successfully hatched them at Pukaha Mount Bruce National Wildlife Centre.
This led to a captive-breeding programme being established at Pukaha Mount Bruce National Wildlife Centre and the Isaac Conservation and Wildlife Trust in Christchurch.
"In the mid-1990s we began moving captive-bred shore plovers onto pest-free islands to establish new populations in the wild," said Houston, who has been working with the shore plover for the past 10 years.
Today there are wild populations of shore plover on four pest-free islands - Rangatira and Mangere islands in the Chathams, Waikawa/Portland Island in Hawke's Bay, and Motutapu.
"Of the total population of 245 shore plover, 220 are living in the wild on pest-free islands," Houston said.
Rangatira is home to 50 breeding pairs of shore plover and is the only self-sustaining wild population. There are 17 breeding pairs of shore plover on Waikawa and six breeding pairs on Motutapu.
Houston said shore plover were very "approachable" birds, which made them particularly vulnerable to predators.
"They will come running up to you to see what is going on. They are great little birds, quite endearing, but is also one of the reasons they are not in places with predators."
Progress on Motutapu had been slow, with the first breeding pairs laying eggs there back in 2015.
However, not many chicks made it through to adulthood.
"We have had up to five chicks fledge there in the past, but last year we had just one."
Given the island was predator free the death rates were proving puzzling to those looking after them.
"We are not sure why they don't make it through. There may be avian predators, like pukeko, gulls or morepork, but we don't know for sure."
This year they had a team of students and volunteers working with DoC staff to monitor the chicks.
'We will be keeping a close eye on the chicks and hope we have a better success rate this year."
Early next year they will be releasing up to 40 chicks bred in captivity, however these had an even lower success rate than those born on the island.
"We have found those born on the island have a much higher chance of survival long term."
Houston said long term they would like to have about 50 breeding pairs on Motutapu and surrounding pest-free islands in the Hauraki Gulf.
"The recovery goal is to have them self-sustaining on five islands - we currently have them on one. I think it will be about another 20 years, all going well, to get to that point."
To keep Motutapu and Rangitoto pest-free, anyone travelling to the islands in a boat, yacht or kayak needs to check their vessel for a mouse, rat or signs of other introduced predators. Cats and dogs are not allowed on pest-free islands.
"We have found even a single rat getting on shore to a pest-free island can have catastrophic consequences," Houston said.
"Anybody visiting the island needs to be really aware about the biosecurity risks."