Once abundant, now endangered

Nā Puawai Swindells

Out of sight, out of mind, a harmful ideology for taonga species who are in dire need of public presence and attention. Mohua, the yellowhead (Mohoua Ochrocephala), is a small, rare endemic bird with a bright yellow head and large powerful feet. They are one of 54 birds listed as taonga species in the Ngāi Tahu Settlement Claims Act 1998, and they are at risk of extinction.

Very few New Zealanders have seen mohua. Field experts from the Department of Conservation (DOC) say there are only two locations left where mohua seem to be doing well – in the Landsborough Valley of South Westland and near the south branch of the Hurunui.

Their low profile, isolation and low genetic diversity make it extremely difficult to manage their recovery. The only place where most New Zealanders will see mohua is on a $100 note.

Conservation Minister Tame Potaka mentioned in a recent interview that it will cost too much to save every single species and that we need to target only those of high value.

However, the whakapapa of te taiao relies on a collective of species to thrive, not individuals. Whakapapa stores key information, a reminder of where things come from, where to find them, when to use them and for what purpose.

Māori can recite whakapapa from the beginning of creation, from the stars to the oceans, from the trees to the birds to the birth of the first human. This knowledge system connects us to our natural environment and everything in it, living as part of a system, not dominating or changing it.

With the whakapapa of mohua all but lost, research is underway to discover more about its identity. The 1920 volume of Traditional Lifeways of the Southern Māori by James Herries Beattie notes the yellowheads or native canaries were known as pōpokotea. Papers past, Pipiwharauroa, Issue 79, published in 1904, lists hihipopokera, momohua, pōpokotea, popotea and upokotea. Te Aka dictionary lists the Māori name for yellowhead as either hihipopokera, momohua or mōhuahua. Pōpokotea, popotea and upokotea are all in reference to the whitehead (mohoua albicilla), a relative of the yellowhead.

The first species recovery plan for mohua was written in 1993 by Colin O’Donell (DOC) and the species recovery group remains active today. It’s made up of Kāi Tahu representatives and Te Rūnanga o Ngāi Tahu technical support, DOC staff and the Mohua Charitable Trust.

The vision is to one day walk away and leave mohua and other species to thrive in their natural environment without intervention.

Colin O’Donell has worked for DOC for over 40 years and remembers being told by a kaumātua in the South Island that tīeke were the kaitiaki of mixed species feeding flocks. The leader of the group, it would guide others in the dislodgment of bark to feed the collective. As tīeke numbers declined, mohua took on the lead role.

Mohua have powerful feet and a boney spine-like tail. They use their features to climb trees and scratch out bark to uncover food. They have been sighted following tīeke on Te Au Moana (Breaksea Island) and will wait for the larger tīeke to rip moss from the tree trunks and boulders, feeding on the leftovers of their larger colleagues.

Their nests also play host to eggs and chicks of koekoeā (long-tailed cuckoos). The koekoeā lay one egg in each mohua nest, and if they find a nest with mohua chicks instead of eggs, they eat the chicks. Koekoeā eggs develop more quickly than mohua, so they usually hatch first.

The koekoeā chick then spends time pushing the mohua eggs and chicks out of the nest.

Mohua eggs in Caitlins; below left: banded Mohua in Caitlins. Photographs: Colin O’Donell

In the 1980s, two mohua nests were recorded with koekoeā in them, but they were unable to eject the mohua. Nesting in the holes of tall beech trees, it can be hard for koekoeā to tip the mohua eggs or chicks out. At this nest, the koekoeā chick gave up and the mohua and koekoeā chicks were raised together. The mohua chick fledged first, probably because they are much smaller, weighing just 25-30g.

Mohua were once the most common forest bird in the South Island. The Hawdon and Eglinton valleys were full of them and there were always yellow-crowned kākāriki and fantails flying with them. Forty years ago there were mohua in the Otehake and Poulter valleys in Arthur’s Pass, Leithen Bush, Burwood Bush, Waikaia, the Longwoods and Rowallan in Southland. But in 2024, they can’t be found at any of these locations.

Intervention methods like stoat and rat eradication, banding, monitoring and translocations have saved small populations from extinction. However, the adaptations of mohua make them extremely vulnerable. When they are laying and incubating their eggs, they don’t leave the nest for weeks. They cannot hear a predator climbing the tree to access their nest until it is too late, and by that time there is no escape because their nest has only one entry/exit point.

Back row, from left to right: Clement Lagrue (DOC), Marion Rhodes (Mohua Charitable Trust), Roselind Cole (DOC), Graeme Elliot (DOC), Kathryn (Kat) Longstaff (DOC), Johanna Kann (DOC), Raewyn Cook (Ngāi Tahu Representative); front: Puawai Swindells-Wallace (Mohua research contractor), Colin O’Donell, Rebecca Teele (DOC). Not in the photo and part of the team: Lisa Thurlow (DOC), and Te Rūnanga o Ngāi Tahu environmental advisers, Jana Hayes and Ben Hodgson. Photograph: The Mohua Species Recovery Group

“We have not figured out how to return them to their former range. With little predator-free habitat left, there is simply not enough forest where they can be protected from stoats and rats. when they are not predated in their nest, they become forest floor snacks when feeding on the ground.”
The Mohua Species Recovery team

In the 1970s, there was a small population on Mt Stokes in the Marlborough Sounds. The population grew to over 100 birds, then in 1999 and 2000 there were two beech tree masting events resulting in an abundance of food and an influx of rats and stoats. Sadly, only four birds (one female) were saved and these were transferred to Nukuwaiata (Chedwode Islands).

One of the biggest problems when trying to regenerate populations is their low genetic diversity.
When conditions are right, these little yellowheads enjoy longevity. Graeme Elliot, a long-time colleague of Colin, and also part of the species recovery team, believes the record for the oldest-known surviving and breeding mohua is 14 years.

According to DOC’s database there was a pair in the Eglinton Valley that lived to 16, but the eggs they produced were infertile during their last few seasons.

The Mohua Species Recovery team notes, “We have not figured out how to return them to their former range. With little predator-free habitat left, there is simply not enough forest where they can be protected from stoats and rats. When they are not predated in their nest, they become forest floor snacks when feeding on the ground.”

When feeding in their winter flocks, mohua scramble up tree trunks and among branches, dislodging moss and bark in a noisy frenzy. Historically, these flocks could number more than 100, and were frequently joined by pīpipi, kākāriki karaka, riroriro, miromiro and pīwakawaka.

Known as a signal of the state of the ngahere, when the mohua are thriving it’s a sign the ecosystem is healthy. If they disappear, it’s a warning the whole forest is struggling.

While iconic birds like kiwi, kākāpō and takahē are incredibly appealing to visitors despite being discrete and nocturnal, there is nothing like experiencing a flock of bright yellow mohua darting through the canopies chatting and interacting and offering an experience that no other bird species can claim.

Puawai Swindells is a taonga species representative working with Hoiho/Takaraha (yellow eyed penguin) and wants to encourage Kāi Tahu whānau whānui to take up the role of kaitiakitaka as a taonga species representative for Ngāi Tahu.

Nesting tree. Photograph: J. Van der Wetering