A natural phenomenon that occurs once every 10 years is likely to be bad news for native birds next year.
Unusually large quantities of flower and seeds are expected in North and South Island beech forests over summer, because of a phenomenon known as beech mast.
More birds are drawn to the food supply, and this in turn generates population increases among predators like rats and stoats.
Kiwi, yellowheads and kakariki are the most threatened bird species, and bats are at greater risk too.
The Department of Conservation says it has a range of programmes targeting the predators under way, but DoC scientist Graeme Elliot warns that with summers now appearing to be warmer because of climate change, beech mast could happen more often.