Conservationists have upped their monitoring of predators and are devising plans to cope with an expected huge surge in pest numbers on the back of the predicted heavy seeding of beech trees.
The situation is raising concerns for the future of the region's fragile native bird populations.
Friends of Rotoiti spokesperson Peter Hale said beech trees periodically produced large amounts of seed in growth years which lead to an explosion in the numbers of rats, mice and stoats.
Numbers of rats and mice increase hugely on the back of the extra food. But it is the rampant killing machines, stoats, which have the last word, increasing their litters as they feed on the extra furry pests before turning their attention to vulnerable native birds when that larder runs dry.
Mr Hale said the most vulnerable birds in the area were the cavity nesters such as kaka and kakariki.
"All ground nesting birds are also at extreme risk so we have grave concerns for the future of the few kea and falcon that are clinging on precariously in the region."
St Arnaud Department of Conservation senior range service-biodiversity Nik Joice said it was a bitter sweet pill for kaka especially as their infrequent breeding is triggered by mast events so they will be under siege when nesting begins.
Friends of Rotoiti members and Department of Conservation staff were discussing strategies to confront the surge in pest numbers, he said.
Mr Hale said that the increase in predator numbers will mean more trapping work for the relatively small band of volunteers and they welcome new members in what is a very rewarding experience.
Friends of Flora chairman Peter Adams said the situation was of real concern.
The voluntary group, which maintained a pest controlled area across 10,000 hectares in Kahurangi National Park, was increasing its pest monitoring and would devise a plan as soon as any increase in pest numbers was evident.
"At the moment there is no feel for how big the problem will be.
"But if it affects us it will affect the rest of the South Island and conservation resources will be stretched to manage it," he said.
To contact FOR visit friendsofrotoiti.org.nz or phone DOC, St Arnaud on 521 1806.
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