Plans for the biggest 1080 drop to date are almost complete and the Department of Conservation will confirm within weeks the exact areas where the poison will be placed in spring.
The Battle For Our Birds programme will spend about $25 million on a poison campaign across 700,000 hectares of conservation land.
DOC scientist Graham Elliot said this year, a beech mast where seedlings from trees litter the forest floor will result in an explosion of rats and stoats that will attack native birds.
"We've never done it on this scale before because we haven't known that 1080 is such an effective tool for controlling rats and stoats until quite recently. We've done some work on it and we've found that 1080, used cleverly, essentially eliminates rats from the forest."
Mr Elliot said the 1080 drop will ensure that native birds will be able to make it through the spring without being killed by predators.
He acknowledged some native birds would be lost to the poison, but said research indicates more survive than if the rats were allowed to live.