No evidence drop wiped out rare birds, agency says.

Claims that the high-profile pest control campaign "Battle For Our Birds" wiped out a group of nationally endangered birds are unfounded, the Department of Conservation says.

The $12 million campaign last year dropped 825 tonnes of toxic bait at sites including Kahurangi National Park on the northwest tip of the South Island, where DoC staff were monitoring a population of 39 rare rock wren at a research site.

DoC staff have now reported that 25 of this group of birds could not be found.

Anti-1080 campaigners claimed the use of 1080 had "exterminated" part of a rare population which the high-profile campaign had been designed to protect.

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New Zealand First conservation spokesman Richard Prosser yesterday reiterated a call for a moratorium on the use of 1080.

But a DoC spokesman said the fact the birds had not been sighted did not mean they had been poisoned.

"We have found no dead rock wren. There's no evidence to suggest that ... we've knocked them out with 1080."

Immediately after the poison operation, 30 of the rock wren population were sighted by the staff monitoring the site.

A large snowfall then made the site inaccessible for two weeks. When staff were able to get back to the area, just 14 were found.

Rock wren were typically reclusive birds, and the DoC spokesman said they were "very flighty" and difficult to monitor.

"We don't know what's happened - whether the heavy snowfall covered the nests or something else. There is a whole host of potential scenarios."

DoC said it would be difficult to measure the health of the population until next year because the birds were no longer nesting and had dispersed.

The total population of rock wren was unknown, but it was listed as "nationally endangered", the second-highest ranking behind "nationally critical".

The "Battle For Our Birds" programme, which began in July, was in response to an unusually large beech flowering season which led to a proliferation of pests such as rats and stoats.

When launching the campaign, former Conservation Minister Nick Smith said major improvements had been made to 1080 use which minimised the impacts on birds or other species.

These included the development of repellents for non-target species.

Rock wren

Small, reclusive birds found in small pockets of the South Island's high country. Their limited flying ability and nesting on the ground makes them easy targets for predators such as rats and stoats.

Population: Unknown
Threat status: Nationally endangered
Source: Department of Conservation.