Native bird numbers have doubled in South Westland thanks to extensive trapping and use of a controversial poison.
The Department of Conservation has been carrying out pest control in the Landsborough Valley for 24 years resulting in the addition of more than 2000 birds.
Fifteen species of native birds now call the area home, including tui, fantails and karearea.
Decades of pest control efforts by the Department of Conservation has seen bird numbers soar. (Source: 1News)
Mohua used to thrive throughout Te Waipounamu before pests were introduced. At first count there were just 14 birds, but there are now 517 of the species in the valley.
Principal Scientist Colin O’Donnell, who leads the research project, said every year at the same time a team walks into the valley to do the big count.
"It still surprises me each year when bird numbers keep going up because we don't know what's 'normal' or how far birds can recover in this environment.
"Mohua were once one of the most common forest birds in the South Island so their recovery in this valley gives us a hint of what forests may have sounded like before the arrival of exotic predators," said O’Donnell.
Bird counter Paul van Klink said the team move throughout the 50 kilometre valley, stopping every 5 minutes to count every bird they see and hear.
"It's a pretty simple technique, it's widely used in New Zealand and we do about 174 counts here over the 2 days," said van Klink.
Te Rūnanga o Makaawhio Pouarahi Kara Edwards said a long term commitment is needed to ensure these kind of results.
"I think that’s been the secret here - you've got a place where concerted effort's been applied over 24 years.
"It gives the whole biodiversity a chance to recover," said Edwards.
Pest control has been key to targeting rats and stoats, with traps set every 200 metres on both sides of the valley.
The controlled pesticide 1080 is also dropped every two years when the beech trees flower, which attract pests.
"That’s the only tool we've got to really control rat numbers at that scale," said Colin O’Donnell.
A similar approach is being used in Canterbury's Arthur's Pass, which has also just reintroduced the mohua.
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