Community pest volunteers monitoring rock wren in the Henderson Basin of Kahurangi National Park say the alpine bird's future depends on the aerial use of 1080.
Alec and Marian Milne, of Golden Bay's Friends of the Cobb, said they had been monitoring a Henderson Basin population of the endangered rock wren during week-long trips into Kahurangi National Park since 2000.
Just prior to Christmas, DOC said 25 monitored rock wren could not be found after the 1080 drop over the Grange Range.
DOC Westport conservation services manager Bob Dickson later clarified the statement saying of the 39 birds being monitored, 30 were sighted directly after the operation but only 14 have since been found.
However, Marian Milne said the birds would not survive without 1080. "Before 2000 there were around 12 pairs of rock wren we were monitoring in the Henderson Basin. Every year we went up there were fewer birds."
Bird numbers continued to drop, despite stoat trapping.
The number of wren in Henderson Basin dropped to two pairs before last year's 1080 drop.
"These birds will be history if nothing is done," she said. "It's not 1080 that's killing them - the stoats are cleaning them out."
Milne said the final two pairs in the Henderson Basin survived the 1080 drop. "We identified five birds before the drop - there are about seven there now."
Fellow Friends of the Cobb volunteer Richard Stocker said the group started the monitoring programme to encourage conservation measures for rock wren. "That was our prime motive."
The group chose the Henderson Basin because a 1986 LandCare Research survey showed 29 pairs of the alpine birds living there - which gave them historic baseline data.
"We chose it as our project in 2000 and since then have watched the population slowly decline until last year when we were down to a couple of pair."
He confirmed more rock wren had been found at the rocky bluff site since the 1080 operation, but the site's geography made it difficult to confirm numbers.
The Friends of the Cobb had run stoat and rat traps across the site for a decade. After significant catches the numbers of trapped stoats and weasels dropped and trapping was discontinued after a decade.
Stocker said the birds nested in crevices in the bluffs and were susceptible to predation from stoats, rats and mice. The population had a relatively high nesting success, but a number of birds died each winter. The reason was unknown but Stocker said it could be down to predation or food competition from mice.
Hundreds of New Zealand bird species needed monitoring, management and research work, but the Friends of the Cobb chose the rock wren because they were near and dear to us, he said.