The biggest 1080 poison drop in New Zealand history gets underway this morning with the Department of Conservation spreading preliminary bait in the Iris Burn Valley in Fiordland.
The department's Battle for Birds programme will eventually drop poison across more than 600,000 hectares of conservation land, which it said is needed to protect endangered native birds.
DOC's Fiordland conservation manager, Lindsay Wilson, said the bait used in today's drop will not be laced with poison.
"The idea of that is to get the rats and possums used to eating the bait, they get a kind of a good experience of eating the bait and then, when we put the toxin out, the uptake of the bait is much better."
Mr Wilson said that will be followed up in about five days with the poisoned bait.
Security is in place on the road to Te Anau airport, where the helicopter used to scatter the bait is located.
The $23 million programme will be carried out across many parts of the country, not just Fiordland.