Mohua, a Ngāi Tahu taonga species, was once one of the most common and noisy birds in South Island beech forests, but today lives in small, scattered populations across about just 5% of its former range.
Roosting and nesting in tree holes, this sparrow-sized bird is very vulnerable to being killed by rats and stoats.
The Department of Conservation targets large-scale predator control to protect key mohua populations and monitors results for this at-risk species.
Monitoring in nine mainland forests last summer showed mohua populations increasing or stable at five sites, but in decline at four others, Doc principal science adviser Graeme Elliott said in a statement.
"We’ve seen small increases in mohua numbers in the Eglinton and Dart valleys in Fiordland and Aspiring national parks, which are the best counts in five years.
"Small populations in Canterbury’s Hawdon and Hurunui valleys remain stable, and the mohua stronghold in South Westland’s Landsborough valley is still trending up despite a drop off in numbers last summer.
"However, it’s a more sobering story in other areas, with mohua numbers in Otago’s Blue Mountains, the Caples Valley, the Catlins and the Grebe Valley in Fiordland continuing to decline."
The results show predator control is making a difference, but also reflects the challenges of keeping rat and stoat levels low enough for mohua to thrive.
A combination of aerial 1080, trapping and ground-based toxins seemed to get the best results, he said.
"This year we’re planning aerial predator control operations at all our key mohua sites to protect them from the surge in predators next year with the widespread South Island beech forest seeding forecast for this summer.
"With their bright yellow head and breast, mohua are our most colourful forest birds, found nowhere else in the world," Mr Elliot said.
"We need to do all we can to keep the chattering of this songbird in our forests."
In the Landsborough, successful predator control has seen mohua go from the brink of extinction to common in the past 26 years.
Last year, numbers dipped due to a beech seed-fuelled rat plague in 2023 taking its toll before the predator control operation in January 2024.
Doc has changed the timing of predator control operations when beech forests seed to before the seeds hit the ground and after they are gone, when toxic bait was more likely to be eaten, which showed improved results. — Allied Media
