The endangered kākāpō species were feared to be wiped out, after a third of its population became critically ill from a respiratory disease.
After months of round the clock care from vets and volunteers, they've made an almost full recovery.
Huhana and Cyndy, two of the sickest birds admitted to Auckland Zoo, have been given the all clear to travel home to Whenua Hou Island tomorrow.
Earlier this year, after a record breeding season, conservationists monitoring kākāpō on the island noticed the birds becoming sick.
Two died, and crisis centres were quickly set up in Dunedin, Palmerston North and Auckland to treat over 35 birds.
Staff at Auckland Zoo have been put through their paces. Nearly 30 critically ill kākāpō were sent for treatment, but Mikayle Wilson told 1 NEWS the outset didn't look good.
"Things were pretty grim."
Vet staff put the birds through CT scans to try and diagnose the illness.
"It's difficult because the birds weren't showing clear signs of pain," she says.
Dr Lydia Uddstrom also spoke with 1 NEWS, recalling the moment they finally found a diagnosis. Aspergillosis - a rare disease only seen once before in a kākāpō in 2012.
"It's a fungal disease that infects the birds' lungs and air sacs with pus, making it hard to breath," she says.
Treatment was an avian equivalent of antibiotics. But because they're so small, the only way they could provide treatment was through a nebulizer, which is a drug delivery device that administers medication in the form of a mist.
Nine kākāpō died, taking the already endangered population down to just 211.
More than 60 CT scans have been performed since April, each one showing more promise.
We put them all through CT scans and we just see the improvement and everyone was just blown away," Ms Wilson told 1 NEWS.
Cyndy and Huhana have been fitted with what the zoo staff call "birdy backpacks" - a transmitter that will easily allow conservationists to find them for check-ups.
They'll catch a passenger flight to Invercargill tomorrow courtesy of Air New Zealand, before being choppered back home.