For decades, the kakapo has been climbing its way back from the brink of extinction.

Luckily, the green parrot, found only in New Zealand, is a good climber. (It has to be, since it cannot fly.) And the bird has had plenty of help from humans who are managing its tiny, but growing, population.

But conservation is complicated work. And according to a study published Thursday in the journal Current Biology, the birds’ centuries-long decline has been accompanied by another, less visible change: Parasites that once depended on the bird have diminished more than scientists would have expected.

That might not seem like such a tragedy, given the low regard most humans hold for parasites. But their role can be more complicated: In some cases, the relationship between host and parasite is mutually beneficial.

And when extinction is a possibility for both parrot and parasite, that relationship warrants further investigation.

“When you’re dealing with extinction and biodiversity loss — of anything — there are impacts we still don’t understand,” said Alexander Boast, an author of the new study and a paleoecologist at the Bioeconomy Science Institute in New Zealand.

“Whether it’s a large, flightless parrot or whether it’s a tapeworm, they all potentially have a role to play,” he added.