A retired Canterbury vet walking down a valley at dusk has delivered the Department of Conservation a piece of news it had almost given up hoping for. Volunteer trapper Hamish Reid heard, then saw, five yellowheads singing in the trees beside the track in the Poulter valley in Arthur’s Pass, four years after a group of the endangered forest songbirds was released there and then seemingly vanished.
The yellowhead, known as mohua, is a small yellow and brown insect-eating bird found only in the forests of the South Island and Stewart Island. It is rated at risk and declining, with fewer than 5,000 birds thought to be left. Once abundant in the 1800s, it was pushed back into a scattering of isolated pockets by forest clearance and by rats, stoats and possums. The bird nests in tree holes, which leaves sitting females and chicks badly exposed when a predator climbs in, and that single habit has done much of the damage over the past 150 years.
That history is what makes Reid’s sighting matter. In 2022, DOC moved 41 mohua from Te Kakahu-o-Tamahia, also called Chalky Island, in Fiordland to the Poulter valley, hoping to seed a new mainland population in a place where predator numbers were being held down. It was a hopeful project. The valley had not held mohua in living memory, and the plan was to give the birds a fresh start on the mainland while offshore island populations acted as an insurance policy. Then the monitoring went quiet. Follow-up checks did not turn up the birds, and the working assumption became that the translocation had failed and the mohua had died out or dispersed.
Reid, who volunteers trapping stoats and rats in the Poulter valley, was not looking for them when he found them. As he told DOC, he was coming back down the valley at the end of a trapping trip when the birds gave themselves away. “On my last trip I was coming back down the valley around dusk when right by the track, five mohua were singing away in the trees,” he said. He knew straight away what he was hearing.
When he passed the news to the rangers, the reaction was not measured. Reid said one staff member “was super excited, jumping up and down”. For a team that had quietly written the population off, the idea that at least some of the released birds had survived four winters and were still holding territory in the valley was a genuine turnaround.
There are two possible explanations, and DOC is comfortable with either. The five birds could be survivors from the original 41, meaning the translocation quietly worked all along and the earlier monitoring simply missed them across a large and difficult valley. Or they could be a mix of survivors and locally bred young, which would mean the birds have not just hung on but have started breeding in the wild. Archie MacFarlane, DOC’s North Canterbury predator control programme lead, summed up the mood in a single line. “Either way it’s fantastic news,” he said.
The birds did not survive on their own. The Poulter and neighbouring Hawdon valleys sit inside one of DOC’s long running predator control areas, worked with a combination of aerial operations and ground trapping, and topped up by volunteers like Reid who run their own trap lines. Mohua are one of the species that shows most clearly whether that work is paying off, because their tree-hole nests fail so badly when rats and stoats are about. Elsewhere, sustained predator control has lifted mohua nesting success from around half of nests to more than 89 percent, so a valley quiet enough for five birds to sit and sing in the open at dusk is a valley where the trapping and baiting is doing its job.
Reid noticed the same thing on the ground. Alongside the mohua he reported hearing and seeing more birdlife generally, including kiwi and ruru, the native owl also called the morepork, which he put down to the pest control across the area. That is the pattern conservationists look for. When the predators come down, it is rarely just the headline species that responds. The whole forest gets louder.
The Poulter release is one of a long line of attempts to rebuild mohua numbers. The species has been shifted onto predator-free offshore islands as a safety net, and mainland releases like this one aim to put the birds back into the kind of beech forest they once filled. The risk on the mainland is always the same. A single bad year, particularly a heavy beech seeding event that sends rat numbers exploding, can wipe out a small population before it has a chance to establish. The near collapse of the well-studied Eglinton valley mohua between 1999 and 2001 is the cautionary tale everyone in the field knows.
For now DOC is not making grand claims. The find is five birds, not a recovered population, and the next step is more monitoring to work out how many mohua are actually in the Poulter, whether they are breeding, and how far they have spread. But it does show that a translocation written off as a failure had life in it after all, and it is a reminder that the slow, unglamorous work of running trap lines up a cold valley in winter is the reason a bird thought gone is still singing there.
You can read the Department of Conservation account of the discovery on Scoop, background on the 2022 release in this 2022 DOC media release, and more about the bird on the DOC yellowhead page.
Have you spotted mohua or other returning native birds in a valley near you, and do you think the predator control is working where you live? Tell us in the comments below.
This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job π
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