A planned 1080 drop in the Dart, Routeburn and Caples Valleys will not occur until "at least" early next month.
In July the Department of Conservation indicated the aerial 1080 predator control operation was likely to be carried out from mid-August, but the "operating window" had been extended by a fortnight.
Doc partnerships ranger Chris Hankin said in the interim the department was continually reviewing several factors, including rodent monitoring, results, availability of resources and weather.
Once a "clear" start date had been determined, public notices would be issued, with landowners, affected businesses and recreation groups to be notified and warning signs erected at track access points.
The valleys are included in 19 sites chosen by the department as part of its next phase of the Battle for our Birds pest control programme, for which the Government had budgeted a total of $20.7million.
The programme includes placement of predator traps, research and consultation and 1080 drops.
The Dart, Rees and Caples drops would include added deer repellent to safeguard deer populations.
