Wetland warriors: a tale of two bittern

Department of Conservation —  27/07/2023 — 1 Comment

Two rare matuku-hūrepo/Australasian bitterns were found emaciated in Te Tonga o Tāmaki Makaurau/South Auckland. It took the work of wildlife experts, iwi and local communities to rehabilitate these young birds, and prepare them for a new home ready for release.

Written by Nicole Steven.

Matuku-hūrepo/Australasian bittern in is rehabilitation enclosure at Auckland Zoo | 📷 Auckland Zoo

One Sunday night in late autumn our on-duty Auckland ranger took a call: a rare matuku-hūrepo/ Australasian Bittern had been found in a backyard in Pukekohe, Auckland. The young female was letting people approach her – strange behaviour for a very secretive, shy species – but showed no outward signs of injury.

After a short stay at Animal Referral Centre, DOC’s Auckland team brought her to Auckland Zoo to rehabilitate. Just over two weeks later a second juvenile female was found in Karaka and brought to Auckland Zoo by BirdCare Aotearoa.

These well-camouflaged birds are an apex predator of wetlands, sharing the top of the food chain with kahu/harrier hawks.

So, what had happened to them?

When these two birds left their nests in summer in search of food, they may have faced strong competition for high-quality food such as tuna (eels), freshwater fish, mudfish, koura (freshwater crayfish), frogs, mice, and invertebrates (such as crickets and beetles).

However, the compounding issue was likely the wet summer that drenched the North Island. This caused widespread flooding and introduced a lot of sediment into waterways – making it tough for visual hunters, like bittern, to see prey in the water.

Without the energy to search further afield for food, health declines quickly. By the time they were found, the two valuable young females were very thin and very thirsty.

Starving bitterns usually die around 350– 450 grams. These two were not far above that weight at around 470 and 570 grams.

The road to recovery

Te Ākitai Waiohua, one of the iwi from the area of where the birds were found, gifted the two young bittern their names. The first was named Te Awanui, relating to a body of water in Pukekohe, and her companion, Hingaia, relating to the Karaka area and connection to Te Ākitai Waiohua.

Under the Zoo vet team’s careful care, with specialist treatment and plenty of nutritious food, Te Awanui and Hingaia steadily gained weight.

Te Awanui went from just 468 grams on arrival at the Zoo to a healthy weight of more than 950 grams, while Hingaia went from 570 grams to more than 800grams.

Hingaia undergoes a health check and treatment at the Zoo | 📷 Auckland Zoo

Zoo vet, Dr Adam Naylor says it was a delicate balance to feed the wild birds.

“Feeding highly malnourished birds like this too much too quickly can cause a condition called ‘re-feeding syndrome’ – severe electrolyte imbalances that can lead to multiple organ failure and even death.

“Conversely, if they don’t get enough food, then they won’t put on weight quickly enough and may succumb to starvation. It’s a delicate balance!”

At the Zoo, the birds self-fed on both live and dead food sources – self feeding being key in natural weight gain and transitioning back to the wild.

Ngā Matukurua: Two birds found under two mountains

Te Ākitai Waiohua recognised the significance between these birds and the two maunga close to where they were found in Tāmaki Makaurau/Auckland; Matukutūreia (McLaughlin’s Mountain) and Matukutūruru (Wiri mountain), known together as Ngā Matukurua. 

Karen Wilson of Te Ākitai Waiohua noted that the names of these mountains mimicked the behaviour of the birds: Matukutūreia is known as standing and watchful, whereas Matukutūruru is known as restful.

When Europeans arrived matuku-hūrepo were abundant in Aotearoa, but now it is rare to see more than one at a time.

Today there are less than 1000 of these ‘Nationally Critical’ birds left in Aotearoa. Habitat loss is a major driver as 90% of wetlands’ habitat has been lost, primarily due to being drained for urbanisation and agriculture.

Planning the release

Emma Williams, DOC’s lead researcher for matuku-hūrepo, and Harry Caley, who leads the operational work for the species, travelled to Auckland to attach transmitters to the two birds.

DOC Science Advisor Emma Williams attaching the transmitter whilst Auckland Zoo vet nurse, Celine Campana held the bird | 📷 Auckland Zoo

Emma says researchers strongly suspect there are more males in the matuku-hūrepo population than females. Making these two females especially important.

“Males are polygynous, meaning they mate with multiple females. Typically, these females would nest closely together within the territory of the male. Yet, we don’t see this behaviour happening much today,” says Emma.

“Most males seem to struggle to settle down and hold territories – instead choosing to move extensively from site to site as if searching for something – a female to mate with perhaps?”

“In populations we’ve examined more closely, there was little evidence that females and nests were present. And in the odd case where a male had settled well, he’d usually only had one female.”

Emma explains that, sadly, this population balance makes sense as females are particularly vulnerable to predators.

“The females are smaller, nest on the ground and are the sole carers of the young – making them particularly vulnerable to cats, dogs, avian predators and pest species like rats, stoats, ferrets, weasels and possums” says Emma.

In general, females are key to increasing bird populations – that’s why these two juvenile birds are so important to the overall population.

Alongside the DOC operations team and iwi partners, our bittern experts searched for a new home.

In the greater wetland complex shared between Waikato, Auckland and Northland, we found just the spot for the Te Awanui to be released: Lake Rotokawau, on the Poutō Peninsula of the Kaipara Harbour.

Preparing for the release in the wetland habitat at Lake Rotokawau | 📷 Department of Conservation

Rotokawau is situated between a system of lakes, most of which have predator control systems put in place. There is plenty of food, and a vast amount of natural resources, as well as a good population of other matuku-hūrepo.

Colin French, Pou Kaitiaki of Te Uri o Hau, which whakapapa to this area, says the area is part of a replanting programme with DOC, Northland Regional Council and the local community, marae and Poutō School.

“We are honoured to be a part of the rehabilitation of the matuku-hūrepo,” says Mr French.

Thanks to conservation efforts, this wonderful wetland will give Te Awanui a good chance of success.

Te Awanui’s big day

When the big day arrived for Te Awanui in late June, Te Ākitai Waiohua handed over the role of kaitiaki of the bird to Te Uri o Hau on the Poutō Peninsula in Northern Kaipara.

These words were shared by David Wilson, Takānini kaumatua of Te Ākitai Waiohua, to send Te Awanui on her way.

He kotuku rerenga tahi

Takina mai te manu o te rangi

Kia mauria koe ki teraa whenua, ki teraa moana

Ko koe ki runga

Ko aau ki raro

To rise to the sky

Grasp the land yonder, Grasp the sea yonder

You up above

And I below.

Filming and sharing our conservation stories with the wider public helps everyone to learn about our native wildlife | 📷 Department of Conservation

On the Poutō Peninsula, the release team and members from Te Uri o Hau gathered together. Following over three hours in the car, Te Awanui was ready to stretch her legs.

Auckland Zoo vet nurse Celine Campana opened the travel case and let the bird take stock of its surroundings.

Releasing Te Awanui into the rich wetland surrounds | 📷 Department of Conservation

She froze.

Standing, watchful.

Five minutes went by.

Just as the team turned their back to retreat – whoosh – she was off disappearing into the reeds and shrubs on the water’s edge.

It was a bittersweet release for Te Awanui. On the day she was set out into the wetland oasis, Hingaia died in her enclosure. A sensitive species, matuku-hūrepo typically don’t do well in human care.

Exploring the wonderful wetland

Since Te Awanui settled in the area, her tracker has sent regular location updates.

Tracking shows that Te Awanui is exploring her surrounds | 📷 DOC

Emma says that it’s looking good for Te Awanui.

“She seems to be foraging a lot more consistently now, which is encouraging.

“She’s almost done an entire sweep of the lake perimeter, so hopefully that’s made her feel a bit more comfortable and confident of where the good food spots are.”

We’re very hopeful for Te Awanui. With her new-gained strength and with the support of the rich surrounds, Te Awanui has a chance to become a successful parent in the years ahead.

How you can help matuku-hūrepo/Australasian bittern

Help wetland ecosystems and species like matuku-hūrepo by:

  • Reporting sightings or callings of matuku-hūrepo to your nearest DOC office
  • Joining community groups undertaking predator control, wetlands plantings schemes, and active listening surveys
  • When visiting parks, beaches, rivers, and lakes:
    – Leave nesting birds alone
    – Only use available access ways
    – Do not drive on riverbeds
    – Learn about the Lead the Way Programme, which encourages dog owners to become wildlife wise and know how to act to protect wildlife
    – Follow the water care road code

One response to Wetland warriors: a tale of two bittern


    Proud of you all. Thank you for your care that allows life for Te Awanui and allows Hingaia to rest in peace. Ngā mihi nui.

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