A critically endangered New Zealand alpine bird's numbers are back on the rise thanks to large scale poisoning of its rat and stoat predators, the Department of Conservation says.

The reclusive rock wren/tuke has recently been spotted in greater numbers at all monitoring sites in Kahurangi National Park on the West Coast.

Its success was a tick of approval for the department's Battle for our Birds aerial 1080 poisoning drop aimed at predators, scientist Dr Graeme Elliott says.
The department this year ran 23 operations with 1080 across 440,000 hectares.

"At one site in the Grange Range, we've seen adult birds increase by more than 300 per cent in the last three years," Dr Elliott said.

"In the area with no predator control, rock wren numbers declined by 90 per cent, until last year when we used aerial 1080 to avoid losing that population."

DOC's Battle for our Birds programme aims to suppress predators, such as rats, stoats and possums to protect the country's most at-risk native birds, bats, lizards, frogs, snails and plants.

In Kahurangi when monitoring began in 2014, 58 per cent of rock wren nests produced young after aerial 1080 was dropped and 45 per cent the following breeding season.

In areas without predator control, just 13 per cent of nests were successful.

Like the rock wren, other species, including kiwi, kea, mohua/yellowhead, bats and native frogs, have also benefited from predator control programmes.
Running until next July, the 2017/18 control programme will cover about 750,000 hectares.