A cry of help for the James Bond of the bird world

It’s still dark when we set off to find what amounts to a needle in a haystack.

“Nice morning,” quips Peter Langlands, a research and photographer, who has just written a book on foraging. “Doesn’t look like there’s much wind, either.”

We’re heading south of Christchurch to a wilderness on the edge of the city – the mouth of the Ararira/LII River (said “L2”), where it drains into the northern shore of Te Waihora/Lake Ellesmere.

Among the bullrushes (raupō), we’re hoping to spy the secretive native bird matuku-hūrepo/Australasian bittern.

On that Wednesday morning, as the sun scythes through the clouds bunched over Banks Peninsula, the only sound competing with the cacophony of birdsong from the lake – from the likes of kakī nui/black swan, tētē/grey teal ducks, and kōtuku ngutupapa/royal spoonbill – is the swishing of our legs through native sedge.

Looking towards Kaitorete Spit, beyond which crashes the Pacific Ocean, there’s a rippling mirage effect.

“The lake’s actually pushed up here in the last week,” Langlands says, as we navigate the channels and drains raking the former farmland like slender fingers.

Some channels are too wide to leap, and the oxygen-deprived mud clutches at our shoes, releasing them, reluctantly, with a squelch, and evil-smelling plumes.

Livestock have been banished from here, and willow trees felled, allowing space for raupō to return.

Days earlier, about 10 kilometres to the east, near where the Halswell River/Huritini meets the lake, Langlands photographed a bittern taking flight.

“I don’t like to visit the same site too close in timeframes,” he says. “The birds are really sensitive to disturbance.”

Hence we trudge towards the raupō bed at the mouth of the LII, which has been reasonably reliable for finding bittern.

The species doesn’t have the profile of kiwi or kākāpō, or even the pūteketeke/Australasian crested grebe, which spectacularly won Forest & Bird’s bird of the century competition.

Since 2018, the bittern has only once managed to sneak into the top 20 of bird of the year – that was in 2022, when it was 19th.

It’s one of 14 bittern species found around the world, but ours are the southern-most. Matuku-hūrepo appear in Māori legends, stories, and place names, and their feathers were used for ceremonial decorations. They were abundant before European colonisation.

Arguably, the stocky birds should resonate more with Aotearoa’s public, given their endearing quirks.

Like kākāpō, the male birds make distinctive booms in breeding season. When startled, they adopt a ‘freeze’ pose, standing tall with erect necks and bills pointing to the sky, swaying in time with the surrounding raupō.

In 2015, this led Nicola Toki, then the Department of Conservation’s (DoC) threatened species ambassador, to say of bittern: “They are masters of disguise; they’re like the James Bond of the bird world.”

Bittern, which are related to herons, used to gather in huge groups around the motu. (The collective nouns for bittern are a pretence, sedge or siege.)

But, like most native bird species, they’re in trouble. The national population has crashed to fewer than 1000 individuals, and it’s no wonder.

They’re wetland-dwellers, and about 90 percent of the country’s wetlands have been drained, for farmland and developing towns. Now, the birds are mostly found in large wetlands in Northland and Waikato, though they are scattered, in low numbers, throughout Te Waipounamu/the South Island.

Their habitat remains under pressure, because of degraded waterways, predators, scant food sources, and, of course, human development.

(Environmental group Love Te Arai mentioned bittern in its successful judicial review of Auckland Council granting consent for a contractor’s yard to operate near the Te Arai stream, which is home to bittern, tara iti/fairy tern, and inanga, the most common whitebait species.)

The Bittern Conservation Trust, of which Langlands is a founding trustee, was registered in October of this past year. Its purpose is “ensuring the stabilisation and subsequent breeding population”.

Langlands has had an interest in bittern since 2009, helping to set up the Department of Conservation’s national bittern database, which led to its classification as nationally critical.

Now, he catalogues the birds in photographic surveys, funded by Canterbury’s regional council, ECan.

Canterbury’s bittern population has remained relatively static for decades, Langlands says, with small numbers of birds generally found in the same locations, year after year. “They’re pretty dispersive.”

He estimates the province has fewer than 50 birds.

However, over the past 12 months, he says bird counts have dwindled at the usual sites – such as along the Waimakariri River and Harts Creek.

A few months ago, Langlands warned in a social media post that bittern chicks had, over years, been found starving, including some on the edge of Te Waihora. He added the dramatic rider: “I feel that we are close to losing this species in Canterbury.”

Department of Conservation fauna science manager Ash Murphy says: “While we know bittern are not doing as well as they could be in Canterbury, and our surveys have shown a decline in the last five years, we do not have evidence to say we are close to losing the species in the region.” 

Says Langlands: “I still consider the species to be on the edge.”

That needle in the haystack – the cryptic birds, with mottled brown and grey feathers that camouflaged them well in raupō – might be harder to find than we thought.

Data deficient

Part of the problem with protecting bittern is how little we know about the enigmatic birds.

The NZ Birds Online website says few bittern nests have been found or studied.

Langlands says the basics of the birds’ population dynamics aren’t known.

“We don’t know the sex ratio of birds. We don’t know the longevity of the birds, or the average age-span of the birds. We don’t know the age of first breeding.”

Their nomadic ways were only revealed by satellite tracking over the summer of 2015-2016 – which mean surveys of males booming in areas quite far apart could be double-counting the same birds.

Yet, bizarrely, these elusive birds will sometimes materialise in people’s backyards, or farms.

Don’t take that as a sign they’re thriving, however.

During a presentation at this past year’s Australasian Bittern Conservation Summit, in Australia, DoC science adviser Emma Williams showcased the 7100ha Whangamarino wetland, between Auckland and Hamilton, which was thought to be the country’s stronghold for bittern.

“It used to have 50-plus bitterns in it and sadly it doesn’t anymore,” Williams said.

Ash Murphy, the aforementioned DoC fauna science manager, says the department’s research into matuku-hūrepo has increased over the past five years, including monitoring the birds’ movements, and identifying important locations.

One focus has been developing new techniques, such as aerial thermal imagery from drones to find adult females and nests. 

“Finding adult females on active nests using thermal imagery is a key priority because we know very little about what goes on at nests. They are very hard to find!”

Murphy lists fundamental, unanswered questions:

• Are the threats the same nationally? 
• Which predators are more likely to visit a nest and destroy it at one wetland (say, in Canterbury) versus another (in Bay of Plenty)?
• How many eggs do contemporary nests have, and does this vary nationally? 
• How many chicks from contemporary nests are successful, and with how many fledglings? 

Langlands, the Canterbury researcher, says the destruction and fragmentation of wetlands habitat in the province is a huge problem. But it also means we know what can be done for bittern – create new, or enlarge existing wetland habitats.

Work is underway.

Near Te Waihora, there’s Ahuriri Lagoon. North of Christchurch sits Tūtaepatu Lagoon, near Woodend, an important site for Ngāi Tahu. The lagoon’s restoration has seen the return of matuku-hūrepo.

And bittern are returning to the Wairarapa.

Arawai Kākāriki (green waterways) is DoC’s flagship wetland conservation and science programme, with five significant sites being restored. However, results aren’t guaranteed.

As previously mentioned, bittern numbers have plummeted at Waikato’s Whangamarino Wetland, despite it being home to about 20 percent of the country’s breeding population of bittern. In 2023, an outbreak of avian botulism there killed thousands of birds.

Another Arawai Kākāriki site, Canterbury’s Ōtūwharekai/Ashburton Lakes, was subject of a damning Ministry for the Environment report, which found the lakes were declining because of too many nutrients from the surrounding land.

The most recent Arawai Kākāriki update, from the 2022-23 season, noted record growth of the key aquatic plant Ruppia in Southland’s Waituna Lagoon. “Catchment action to address nutrient and sediment inputs also remains critical to restore the lagoon to a healthy state.”

Meanwhile, Canterbury’s regional council funds predator control and bittern monitoring around Te Waihora. Shaun Burkett, ECan’s biodiversity leader, says its focus is on habitat.

“We don’t know the current bittern population trends with any certainty (but are keen to know).”

In its latest long-term plan, ECan, the regional council, has proposed a new targeted rate for “landscape-scale indigenous biodiversity” work, to protect priority habitat. It’s hoping to raise $1 million.

Langlands says: “We need relatively large wetland habitats created for the birds that produce a reliable food source.”

The relationship between wetlands and bittern is two-way, he suggests, as the presence of matuku-hūrepo is an indicator of a healthy environment. “If the bittern aren’t [there] we know something’s not working too well.”

“A healthy calling male does not indicate successful breeding.”

Ash Murphy, Department of Conservation

As we near the LII River, Langlands points to a stand of raupō: “We’ll have up to about three male birds booming in this area in the springtime.” However, at other times of the year birds move from the lake to feed. “That’s why it might be a bit hit and miss encountering a bird today.”

He whips the camera to his eye. Click-click-click-click-click. A royal spoonbill, that one. Further along, more clicks. A tara/caspian tern.

We trudge further. Langlands shakes his head.

“It’s prime feeding habitat for bittern in here: nice shallow edge, presence of eels, reeds nearby. It doesn’t get any better than this, to be honest.”

Where willows once dominated, raupō is starting to take over. The LII, Langlands says, is one of the healthiest rivers flowing into Te Waihora. “It has very clean spring water, and it’s got relatively good fish populations in it, too.”

DoC provides a comparison to show how low bittern numbers are in Canterbury.

Data collected over the past five years, from automated monitored sites in the province, recorded average male bittern calls of 0.53 per 15 minutes. By contrast, an “extremely active” Waikato wetland site had 7.2 calls per 15 minutes, recorded over a three-year period.

“It’s important to understand that currently all our monitoring around Christchurch is for male bittern as they are the only ones that call in the breeding season,” Murphy, of DoC, says. “We cannot be clear on how much breeding is occurring in the region. A healthy calling male does not indicate successful breeding.”

DoC hopes to expand its aerial thermal drone surveys in Canterbury and the West Coast to include adult females in the coming breeding season.

There’s a caveat, though, which takes on extra weight in the current political environment. “The work programme for next season is not confirmed yet,” Murphy says.

It is a luckless Wednesday.

Langlands and I find no bittern in the raupō beds at the mouth of the LII. We amble along Te Waihora’s mudflats, returning stranded tuna/eels into channels as we go.

The disappointed researcher is anxious to hear booming in this area, come spring.

“You’ve got one of their best breeding strongholds, one of the core populations, you’ve got reed beds, you’ve got channels, you’ve got a proliferation of eels, we’ve come out at dawn at the best time to see them, being a crepuscular [active at twilight] bird, and there’s nothing here,” he laments.

“Just unbelievable, to be honest. We’ve got other birds: we’ve got herons, egrets, spoonbills, but no bittern.

“So, Elvis has left the building.”