The 1080 poison programme in Mt Aspiring National Park starts at 5am today, weather permitting.
Helicopters following a GPS-controlled flight path are dropping non-toxic pellets to rats, mice and possums in the east and west branches of the Matukituki Valley.
The ''pre-feed'' is designed to get rodents and possums used to eating pellets so they will be less wary of those containing 1080 when they are dropped later this month or early next month.
The non-toxic pellets are 3cm long, cylinder-shaped and brown. They weigh about 6g.
The pellets are deployed at the rate of 1kg per hectare, or one pellet per 60sq m of land.
The toxic pellets, dyed green, will be applied in the same areas as the pre-feed.
All the walking tracks in affected the valleys are closed for up to 24 hours during the pre-feed and the toxic drop.
Immediately after each drop, tracks will be inspected by Department of Conservation staff and cleared of pellets.
Another operation will be mounted in the Makarora Valley, and ultimately 46,000ha will be covered in the park's Matukituki, Cameron, Young, Blue, Makarora, Siberia and Wilkin valleys.
The poisoning is part of Doc's ''Battle for our Birds'' programme, covering 700,000ha, designed to reduce the number of predators putting native birds at risk.
Doc's Wanaka service manager Chris Sydney said yesterday birds such as kea were expected to ''thrive'' as a result of the programme.
Stoats were the biggest threat to ground-nesting kea. While they do not eat the pellets, they do eat the carcasses of rats, mice and possums containing the 1080.
