Fungus threat to rare native bird

By ANNE BESTON environment reporter

Often, more questions than answers are raised in the battle to save New Zealand's most precious birds.

But pioneering work on the impact of disease on native species is making the picture even more complex.

Scientists and conservationists have wondered for decades how much disease has affected the likes of the bellbird and the stitchbird, or hihi.

Their rapid disappearance from mainland New Zealand seemed to point to a catastrophe, of some kind, possibly explained by their exposure to new diseases brought by European settlement.

Now a Massey University PhD student has a theory on why a hihi transfer to Mokoia Island, in Lake Rotorua, is on the brink of failure and the ramifications that might have for bird conservation.

John Perrott is a man with a mission. The 33-year-old talks with unbounded enthusiasm of his work, studying hihi on Mokoia since 1994.

Once common all over the North Island, hihi vanished as early as the 1880s. Little Barrier Island, their last self-sustaining refuge, has about 4000 birds.

Hihi (Notiomystis cincta) are starling-sized nectar-feeders. Maori ate them and used the male's yellow breast feathers to ornament cloaks. They are territorial and build their nests high in the forest in mature native trees such as the puriri.

The transfer of 40 adult birds to Mokoia was a bid to save them from extinction. About 50 to 60 birds live on Tiritiri Matangi, in the Hauraki Gulf, but that population, and another small group of birds on Kapiti Island, near Wellington, are fragile.

In the six years since hihi were taken to Mokoia Island, more than half have died. Mr Perrott believes they will disappear from the island in five to 10 years. Post-mortems of 10 showed the fungal disease aspergillosis was the most common cause of death.

Aspergillosis is a respiratory disease caused by the aspergillus fungus, the same dark fungus which grows on stale bread. It is common in the environment, but Mr Perrott's theory is that hihi are particularly prone to high levels of it.

In disturbed or regenerating forest, such as that on Mokoia Island, he found elevated levels of aspergillus mould.

The theory is that aspergillus thrives in disturbed forests, which have higher daytime and lower night temperatures than mature forest. In that environment fungi which keep aspergillus in check don't thrive. Mr Perrott thinks hihi might be aspergillosis susceptible because they nest in damp tree cavities where the fungus thrives. They also have a long nesting period and feed their chicks on cicadas - Mr Perrott found the disease in Mokoia cicadas and believes that is one way the fungus comes in contact with the birds.

"If this disease is linked to deforestation, then they may have historically had very little contact with it," he says. "Their decline on the mainland coincided with the most intensive logging period in our history."

Aspergillosis contains alfltoxicosis, one of the most carcinogenic substances known. Once the birds are over-exposed to the fungal spore, their infected lungs develop greyish-white nodules which then move to the brain. Dying hihi wheeze instead of making their "tee-tee-tee" cry.

After completing his Master of Science degree with first class honours, Mr Perrott began his PhD in 1994, but extended it to finish his work on hihi. He is now seeking finance to carry on his research, which has been published here and overseas.

In November, he will move to Little Barrier Island to compare its fungal counts and living conditions with Mokoia to try to find answers to the hihi's struggles there.

"The situation is critical. They are officially classed as vulnerable but it's much worse than that."