A respiratory disease called aspergillosis has killed four kākāpō chicks and two adult females within a month and a DOC scientist says it could set back recovery efforts for the critically endangered bird.
DOC scientist Andrew Digby told TVNZ1's Breakfast they are not completely sure what has caused the rise in deaths due to the disease but they do have some theories.
"It affects the kākāpō when their immune system is compromised," he explained. "It could be the result of the female kākāpō doing a lot of effort nesting, an underlying disease, or it could just be there are loads of it in the environment this year and it's really heavy loads they can't quite cope with."
Mr Digby said the disease is very hard to treat and they can't diagnose the birds without them having a CT scan.
Twenty kākāpō have been taken to the mainland to get tests. Five have aspergillosis and two are at real risk of dying. The other 15 are still to get tested.
"We know all of the birds individually so it does hit hard each and every one," Mr Digby said. "They are on the brink of extinction and this sort of thing could really set back the recovery efforts."