Head wildlife keeper Paul Kavanagh said the species, found only on Antipodes Island, 860km southeast of Stewart Island, was the subject of a national captive breeding programme to create a back-up population.
"It would only take one disease outbreak or one predator outbreak and they would be extinct," he said. "It's really important to have a captive breeding population as an insurance policy."
Cleo, whose male companion died earlier this year, was removed while volunteers added a pond, rocks and nesting box.
She was then introduced to bachelor Banner, from the Te Anau Doc Centre, and together they were introduced into the revamped enclosure to put them on an even footing. Mr Kavanagh said the signs were promising.
If the couple produce offspring, they will be coupled with other parakeets across the country to maintain bloodline diversity.
