The director of the Cook Islands Natural Heritage Trust says as the mynah bird population on Atiu goes down, coconut stick insect numbers are going up again.
Gerald McCormack says he is confident an 80,000 US dollar programme to eradicate the invasive Asian bird species will have succeeded by about mid-year and a new priority is to ensure the shiprat doesn't reach the island.
Mynah numbers grew into the thousands after introduction in the early 20th century and the bird, which is very territorial, had a huge impact on species of native bird.
But Mr McCormack says the mynah was brought in to control the coconut stick insect and it did that very well.
"There certainly is though a lot of stick insects on Atiu at present. I've never been very successful in finding them at night, partly because I'm colour blind but when I go out in Atiu with my torch I can see several under every palm just about."
Gerald McCormack says trees affected by the stick insect appear to be recovering but if numbers get too high, the mynah bird can always be reintroduced.