The population of kākā in a North Island forest is soaring, having quadrupled over the last 20 years, according to long-term Department of Conservation monitoring.
The native parrot is classified as at risk but recovering.
Twenty years ago at Pureora Forest, in the Waikato, there were around 640 birds.
DOC says there are now around 2600 kākā in the forest as of October.
"This is a very impressive result from our work to protect this species over the past 20 years," DOC science adviser Terry Greene says.
"Our observers also noted plenty of other birdlife in the area - a very positive sign our long-term conservation and predator control work is paying off."
Kākā and other birdlife in the forest are threatened by pests including stoats and possums.
Aerial and ground predator control, including the use of 1080, has taken place in the area.
Te Hau Kainga o Pureora secretary Frances Hughes says it's important that predator control work continues so the forest is able to flourish.
"We have a beautiful pristine forest, amplified with the loud calls of the kākā and the beautiful chorus of the kōkako, tūī, toutouwai, and many, many others, that remind us of our childhood days," she says.
"Predator control must remain in place, be maintained and developed regularly, to combat the resistance and behavioural patterns of these predators, to totally eradicate them."