The endangered kākāpō bird is falling victim to a fungal disease.

Department of Conservation kākāpō operations manager Deidre Vercoe told Mike Hosking although they have just come of the back of an incredible breeding season for the kakapo, the aspergillosis disease is starting to hurt the kākāpō population.

"This has been the best season on record, there have been 86 chicks which have hatched. Unfortunately, we have gone to some dark lows with a disease which has come, we have lost six birds in the last six weeks."

Vercoe says the disease is extremely hard to detect and by the time it has been diagnosed, it is often too late.

"The birds look healthy until only a few days before they die. We have to send them off to the offshore islands for treatment which can be a difficult process. We are doing the utmost we can to look after the birds"

Kākāpō birds with low immunity could succumb to respiratory disease if exposed to high doses of spores.