Many of the Mercury Islands off the Coromandel coast are predator-free and rangers from the Department of Conservation (DoC) are working hard to keep them that way.
As holidaymakers flock back to the region and boaties hit the water, there are concerns their work will be jeopardised.
They took Newshub reporter Kethaki Masilamani to an undisclosed island where people are usually prohibited from visiting.
Island ranger Darcie Bellanto has a lot of tools in her arsenal to help with biosecurity.
"These scrubbing brushes are for getting dirt off boots," she says.
She pores over every inch of equipment and clothing, looking for foreign seeds and scrubbing off dirt - anything that could threaten native life on the Mercury Islands.
"By keeping the islands pest-free we're actually enabling these birds and these species to thrive on these islands," Bellanto tells Newshub.
The DoC rangers are among a handful of people allowed onto the islands. Newshub won't name this one because DoC doesn't want any uninvited guests.
Today, they're checking on some artificial burrows that were installed in partnership with the Northern Seabird Trust earlier this year.
"When we're putting them in it was a hot long day, we were sweaty and covered in dirt so it's exciting to see they've got little critters in them now," community ranger Amy Blair says.
The little critters are fluttering shearwaters and the boxes are a little more convenient for both birds and the people who look out for them.
"The scientists can just lift the lids off the burrows and try and look at the birds without causing too much stress," Bellanto says.
Fluttering shearwaters don't tend to fly very far and rely on nearby food sources to survive. They're used as indicator birds - a barometer for biodiversity on the island.
"By monitoring their health and their development we can get a pretty good idea of what's happening locally in the terrestrial and marine environment," Bellanto says.
But their survival relies on keeping pests off the island - a challenge as people flock to the Coromandel over summer.
Most of the eastern Coromandel islands are predator-free and to visit them you need special permission from DoC. Even anchoring your boat to close can have its risks.
"A rat can swim pretty far, a lot further than people think so observe from a distance, swim in the water but stay off," Blair says.
Because life on the islands is considered a taonga, a gift to local iwi and the rangers themselves.
"I feel like a kid at Christmas time," Blair says.
"I love opening the little boxers and seeing the chicks inside, they've got so much character and I love it," Bellanto adds.
Because if left alone there can be life on Mercury.
