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Displaying items by tag: Bittern

Saturday, 17 February 2024 21:27

Elusive Bittern

Elusive Bittern caught on camera at Wairio Wetland

Jessica Wagner is a student at Victoria University of Wellington, researching rat response to scent and acoustic stimuli in the Wairio wetland. The intended outcome of Jessica's research is to determine what stimuli are most attractive to rats in order to improve trapping efforts, and ultimately, to protect rare birds such as the Bittern and wetlands in general.
Jessica was a recipient of one of the wetland care scholarships.

"I was recently going through my footage and noticed that one of my cameras has recorded a video of a Bittern on the 4th of December! I thought that you and others at Ducks Unlimited NZ may be interested in this so I have attached the video below. Feel free to share with anyone else who may be interested" (Jessica) .

Published in Wairio News

First recorded booming within the DU Wairio wetland

The spring 2022 survey report compiled by Shane Cotter, a contractor engaged by GWRC.

John Cheyne of Wetlands Works led annual spring surveys for Australasian bittern (matuku, Botaurus poiciloptilus) and spotless crake (pūweto, Zapornia tabuensis) at selected wetlands within Wairarapa Moana between 2012 and 2021. In 2022, John passed this responsibility to me. I conducted the annual spring (October-November) 2022 survey using the same methodology as in previous years so continued comparisons could be made of the annual results.

This year’s survey focused on the core wetlands (Boggy Pond, Matthew’s Lagoon and Wairio wetland) and the northern wetlands (Barton’s Lagoon, Tauherenikau delta, Simmond’s Lagoon, JK Donald Block). Only booming male matuku are surveyed because females are much less vocal and therefore very difficult to detect and monitor. This booming call is associated with males attempting to attract females for breeding. Pūweto were also surveyed at Boggy Pond and Matthew’s Lagoon.

In the 2022 survey, 11 booming male matuku were located at the core wetlands and 12 in the northern wetlands. This is an increase in previous years and a record number at both locations. At the core wetlands, numbers have remained relatively stable at 8-9 birds since 2014 while at the northern wetlands, annual numbers of male matuku has varied between 3-9 birds. Overall, the combined number of booming male matuku at the core and northern wetlands has steadily increased from 10 in 2016, to 16 in 2018, to 18 in 2020, and now 23 birds in 2022. In addition to the 23 male matuku heard booming during the 2022 survey, three other birds were seen, one in Matthew’s Lagoon near Boggy Pond and two in Wairio wetland.

At Boggy Pond, nine pūweto were located, the most in Boggy Pond since 2018 and significantly up on the single individual in 2021. At Matthew’s Lagoon, none were recorded during the kayak survey which has been a regular result there since 2014. While undertaking the matuku survey, four other pūweto were heard calling independently, not in response to playback calls. Two were calling in Matthew’s Lagoon close to each other while at two locations within Wairio wetland, one individual was heard calling. I believe there are more pūweto present than recorded during the pūweto surveys. They have just moved to different areas of the wetland complex outside the pūweto survey routes seeking more suitable habitat.

On-going predator trapping with the regular servicing of traps is essential as several predators were seen dead in traps within days of the traps being serviced and rebaited with fresh bait by the trapping contractor at the core wetlands. These included a weasel and several rats. All traps observed were well set up and maintained, and had good vegetation clearance.

Follow the 'read more' link to view the survey report.

Published in Wairio News
Friday, 13 March 2020 08:58

Kimi's special high country mission

Kimi, the world's only bittern dog, recently took a break from her usual job of looking for bitterns to take on a special role for her best friend, DU Director Emma Williams. She was to be ring bearer at Emma and bat expert Colin O'Donnell's wedding.

The couple were married on 3 January at Criffen Station, a high country station in Wanaka. We assume bitterns and bats are regular breakfast conversations for the newlyweds.

Congratulations Emma and Colin.

Published in Issue 178
Tagged under
Saturday, 09 November 2019 22:42

Bittern steals the show

Ducks Unlimited recently received a substantial donation to put towards its restoration work at Wairio Wetland.

Janet and Patrick Velvin, who live in South Wairarapa, are passionate about conservation, particularly water conservation, and contacted The Gift Trust, a philanthropic advisory service, to identify suitable causes they could support.

Cheryl Spain, executive director of The Gift Trust, said they had been impressed with the research on Wairio and DU’s partnerships with the Department of Conservation, Greater Wellington Regional Council and Victoria University, particularly its links with the student research projects at Wairio, and had chosen Wairio as a suitable recipient.

The Velvins visited the wetland for the first time and took part in a planting day with Victoria Uni students in early July.

After helping with the planting, they were given a guided side-by-side tour by Ross Cottle, who identified a suitable site on a promontory for a viewing hide, which could be constructed with some of the funds donated by the Velvins.

During the tour, Patrick asked if there were bitterns in the wetland, and as if on cue, a bittern obliged and flew in front of the them.

Janet became aware of the work at Wairio Wetland through the book Wairarapa Moana: The Lake and its People.

Janet said after the tour they were impressed with Ducks Unlimited and happy to give a donation towards the work at Wairio.


Published in Issue 177
Tagged under
Tuesday, 27 August 2019 17:00

The Bitterns are a Booming

Bitterns are an iconic wetland bird which is becoming increasingly rare through wetland loss and predation by mammalian predators.

They are the apex avian predator in many  wetlands and their presence gives an indication of overall wetland condition and health.

I was fortunate that Greater Wellington Regional Council engaged me last year through my small wetland consultancy WetlandWorks to carry out wetland bird surveys on a number of wetlands on the eastern side of Lake Wairarapa. This included Boggy Pond, Mathews Lagoon, Wairio wetland, JK Donald Block and Bartons Lagoon. 

Each trip was 8-10 days duration and we based ourselves at Kilmore Lodge, a great home away from home owned by Wellington Fish and Game. One of my recommendations to the Council was the need to carry out a  bittern survey of all wetlands around the lake to get a good handle on the population and what threats each site was subject to.

The survey, carried out over two weeks in  October and November 2013, focused on  locating male bittern who in spring advertise their presence by making a booming call much like a fog horn. They establish territories in mainly dense raupo and use this call to  advertise their presence to available females and make other males aware not to come near. The main calling periods are one hour either side of sunrise and sunset. Occasionally they boom all night and all day when there is plenty of action on. This requires regular early starts and late finishes for the bittern counters.

During the survey 20 male bittern were recorded booming and their territories plotted on a map. Seventeen of the booming birds were calling from patches of raupo and the other three from scattered wet patches of oioi (jointed rush), closer to the eastern lake edge. 

The main concentrations were around five key sites: Boggy/Mathews/Wairio, Ponui Lagoon, Barrage Gates, south Donald/Mangatete Stream and Bartons/Tauherenikau River mouth.

While bittern are polygamous and males can  attract more than one female to their territory, some males are unsuccessful at attracting any. Other studies indicate the sex ratio is about 1:1 so the total population for Wairarapa Moana and associated wetlands is around 40 birds. A report is currently being prepared for Greater Wellington Regional Council that will discuss how these wetlands can be better managed for bittern.

Bittern Workshop

A “meeting of the minds” for people working on bittern was held at Kilmore Lodge, Boggy Pond, Wairarapa on November 2 last year. This was attended by the DOC bittern scientist from Christchurch, other DOC staff, a university  student doing a doctorate on bittern, and Greater Wellington Regional Council staff.

This was followed by a get together of local people and landowners interested in bittern around Wairarapa Moana. About 25 people overall.

The presentations and discussions that followed focused on the biology of bittern, habitat use and threats from plant and animal pests and was followed by a short trip to the Boggy Pond car park where everyone heard three of the local male bittern booming and advertising their wares.

A great opportunity for everyone to share information on this threatened but still keystone wetland bird.

John Cheyne



Published in Issue 158
Tagged under
Monday, 22 July 2019 11:46

Winter shorebird survey

Winter shorebird survey results at Lake Wairarapa

Steve Playle, Hugh Robertson and Nikki McArthur took advantage of excellent weather conditions on June 20 to carry out a winter shorebird census at Lake Wairarapa. The water level was relatively high (10.3 metres above datum), so most of the mudflats were under water and in turn that influenced some of the 
species counts.
By the end of the day they had counted 22 species of shorebirds and waterfowl, totalling 5647 birds. Highlights of the day included four Australasian bittern, two white herons and a little egret (the latter a relatively rare Australian vagrant). Hugh encountered a flock of 122 red-billed gulls at the Oporua Floodway, which 
is exceedingly unusual for this site. Red-billed gulls are extremely rare visitors to Lake Wairarapa, having been reported only a handful of times previously (11 birds in February 1948, “irregularly” between 1982-1983, 2 birds in April 1992 and 1 bird in February 2012).
A full summary of the species counted during June 20 census follows. For anyone who wishes to test their bird ID skills, or read background about any of the species recorded go to New Zealand (NZ) Birds Online website (
Black Shag
Little Black Shag
Little Shag
White-faced Heron
White Heron
Little Egret
Royal Spoonbill
Black Swan
Canada Goose 
Feral Goose
Paradise Shelduck
Variable Oystercatcher
Pied Stilt
Banded Dotterel
Black-fronted Dotterel
Spur-winged Plover
Black-backed Gull
Red-billed Gull
Black-billed Gull
Caspian Tern

This is the third winter survey since initiating this work in 2011, so it’s now possible tobegin comparing average species counts from June 2011-2014 surveys with those from Hugh Robertson and Barrie Heather’s earlier set of surveys carried out between 1985 and 1994, for the section of shoreline between the Tauherenikau Delta and the Oporua Floodway. These comparisons give an early indication of some of the changes that appear to have occurred to the relative abundance of various bird species at the lake over the past 30
years. A number of species appear to have increased in abundance over the intervening time, among them NZ dabchick, black shag, little black shag, little shag, black-fronted dotterel and black billed gull. A smaller number of species appeared to have declined in abundance over the same period, including SI pied oystercatcher, pied stilt and spur-winged plover.
Black Shag 
Little Black Shag 
Little Shag
Pied Shag
White-faced Heron 
White Heron
Cattle Egret
Glossy Ibis 
Royal Spoonbill 
Black Swan 
Canada Goose
Feral Goose
Paradise Shelduck 
Pied Oystercatcher 
Variable Oystercatcher
Pied Stilt 
Banded Dotterel
Black-fronted Dotterel
Spur-winged Plover
Sharp-tailed Sandpiper
Bar-tailed Godwit
Black-backed Gull
Red-billed gull  
Black-billed Gull
Caspian Tern
Average count 
2 15.0
Average count


Nikki explained the original aims of this survey work were relatively simple (i.e. to give the ability to describe changes that have occurredin the lake’s bird fauna over the past 30 years;

to allow them to detect future changes and to re-examine the relationship between shorebird abundance and water levels). You might be interested to know the data from these surveys have recently been put to a variety of other
uses, including:

• To provide quantitative evidence in support of an application to have the Wairarapa Moana wetlands recognised as a “wetland of international importance” under the Ramsar Convention.

• To provide evidence to support the Wairarapa Moana Wetlands (together with
the Ruamahanga River) being listed as an “Important Bird Area” under Birdlife 
International’s global IBA programme.

• To form part of our flood protection department’s programme for monitoring
the health of riverbed-dependent bird populations on rivers affected by flood 
protection activities (large proportions of the regional populations of several riverbed-dependent bird species overwinter at Lake Wairarapa).

• To provide regional population estimates for a number of shorebird species used for the development of a regional threat classification system for birds of the Wellington Region.

• And lastly, data collected during these surveys are combined with data compiled from other key shorebird sites around NZ to provide estimates of the national population sizes of a number of NZ’s shorebird species. These national 
population estimates are in turn put to a variety of uses, including a regular review of national threat classification rankings and ongoing monitoring of the population health of Arctic-breeding migrants using the East Asian/Australasian Flyway, a major avian migration route stretching from Alaska and Siberia in the north to NZ and Australia in the south.
Thanks go to Ian Gunn, Tony Silbery and Bob Green for assistance preparing for this survey, and to Bob Green, Grant McGhie, Graham Field and Tim Loe for permission to access various points of the shoreline. The next scheduled shorebird survey at Lake Wairarapa is for November 2014.

Nikki McArthur
Environmental Scientist
Greater Wellington Regional Council


Published in Issue 161
Tuesday, 02 April 2019 21:18

Trans-Tasman bittern knowledge exchange

Australian wildlife ecologist and bittern expert Matt Herring visited last year and took the time to catch up with his New Zealand counterparts.

“The best thing we can do for nature is simply spend more time in it. From there, reverence grows and action flows.” M Herring, 2013

What a wonderful trip. It was as if we spent a week compiling precious pieces of a rare, incomplete jigsaw puzzle called “Australasian Bittern Ecology and Conservation”. 

After several years of being in touch via email and phone, it was so nice to finally get together with the New Zealand bittern crew and see some of their sites first hand. 

There is some great work happening across the ditch and a strong sense of being united in working towards reversing the decline of this iconic waterbird that we share. It is affectionately known as matuku hūrepo in Māori, or matuku for short.

The knowledge exchange began with the biennial National Wetland Restoration Symposium in Napier where I was honoured to be a keynote speaker, focusing on the importance of community engagement, novel habitats and active management.

We then had a day visiting wetlands around Hawke’s Bay, including Pekapeka Swamp, followed by a successful bittern workshop day organised by Matt Brady from DOC. It was now crystal clear to me that there’s a lot of love for matuku in New Zealand. 

With much discussion about wetland restoration targeting bitterns, it was astounding for many folk to learn about bitterns in rice and how bare, ploughed paddocks ready for sowing are able to support nesting bitterns less than three months later. There was a range of inspiring case studies from around New Zealand at the workshop, and we got to visit some local work in Hawke’s Bay with Hans Rook.
After that, it was time to begin a broader tour of bittern sites across the North Island. First stop was Lake Whatuma, and thanks to John Cheyne and Bernie Kelly, we were able to track some bitterns while kayaking. 

We discussed key issues like willow control, raupo (cumbungi) harriers as bittern nest predators. 

This wetland has up to nine booming males, but far fewer females, perhaps only three. The apparent shortage of female bitterns across New Zealand is something DOC’s Emma Williams is very concerned about. We may well have the same problem in Australia. 

males in rice fields have up to three nesting females in a single territory, there is emerging evidence that would support a general shortage of females here too. It’s definitely something we should consider: a booming male may not be a sufficient indicator of breeding 
or site quality.

It was now October and time to visit the 7200-hectare Whangamarino Wetland, between Auckland and Hamilton. This Ramsar site was once the world’s most important wetland for the Australasian bittern, with more than 140 booming males in 1980. 

Nowadays, there’s only about a dozen. I learnt about the many issues that are implicated in the decline, such as introduced species and water quality, but I think the huge water level fluctuations are central.

Near Tauranga, we visited the Lower Kaituna Wetland, and were lucky enough to spot a bittern feeding in the eleocharis. Part of the restoration work in the broader area is starting from scratch, essentially constructing new wetlands. 

And on the edge of Tauranga itself, right on the coast, we visited a bittern breeding site that was tidal. This was quite perplexing. The vegetation is low and we wondered where they build their nests without being flooded. 

Unfledged chicks have been found in land nearby, including a recreational park. We talked about how this site would be suitable for a thermal drone in locating nests and monitoring breeding success.

All in all, a wonderful trip, with special thanks to all who made it possible. I’m looking forward to returning the favour! 

The love for matuku in New Zealand is admirable, and the conservation work being done is inspiring



Published in Issue 176
Tagged under
Tuesday, 02 April 2019 21:16

Bittern count reassessed

New research highlights the importance of New Zealand’s wetlands for one of our most secretive native birds, the Australasian bittern or matuku, Conservation Minister Eugenie Sage said on World Wetlands Day, 2 February.

GPS tracking of matuku/bittern has, for the first time, revealed that it flies more than 300km between wetlands in the eastern South Island as well as large distances between North Island wetland sites. 

Previously it was thought bittern ranged only small distances from their home wetlands.

DU is one of several partners in the Department of Conservation-led research, which shows that bittern rely on a network of wetlands to feed and breed in. 

It also means matuku/bittern may be rarer than previously thought as birds have probably been double-counted in local counts in different parts of the country.

In the study, male bittern were tracked flying 330km from Te Waihora/Lake Ellesmere in Canterbury to wetlands near Blenheim during the breeding season last spring. 

They also flew 117km from Whangamarino wetland in north Waikato to south Kaipara and from Whangamarino to Kaituna in the Bay of Plenty.

Published in Issue 176
Sunday, 31 March 2019 21:35

DU director takes up DOC role

DU director and bittern expert Emma Williams’ workload has become a whole lot busier after she was appointed science advisor (wetland birds) for the Department of Conservation in October.

A fulltime job for four years, her main task is to deliver the national bittern research plan. The role also involves work with other wetland birds such as spotless crakes and marsh crakes with the aim of setting up new collaborations with organisations to try to fill some of the knowledge gaps about cryptic and native wetland birds.

Projects include working with Stephen Hartley and students at Victoria University in Wairarapa Moana. One of the current projects involves putting out artificial bittern nests in several study sites, including Wairio, to determine what predators are targeting bitterns.

Emma says new bittern monitoring projects in South Kaipara, Auckland region, Tauranga and Turangi are expanding DOC’s national monitoring reach. The goal is to identify where bittern strongholds and hot spots are and inform where new projects are needed to try to reverse bittern declines.

Published in Issue 176
Thursday, 12 April 2018 16:10

The secret life of male bitterns

Finally revealed by DU transmitters

Last issue I introduced Australasian bitterns, a rare, secretive wetland bird that often lives within a stones’ throw of people’s houses – yet only the lucky few who spend time in wetlands know this species exists!
As our  bittern is the rarest in the world, we have  several reasons to be concerned about the population here in New Zealand.
In the last DU issue I discussed several threats known to limit bittern populations overseas - threats that are unfortunately also present in New Zealand. These threats include habitat loss (here in NZ this loss amounts to a shocking 90 percent!), introduced predators, modified water levels, poor water quality and inconsistent food availability. Unfortunately, despite knowing this, we still have little information about what’s happening with the bittern population here in New Zealand.
This is mainly because bitterns are almost impossible to find and study due to their camoflage plumage and elusive behaviour. Not being able to find this species also means conservationists can’t tell if their efforts to save the species are working.
To solve this problem we’ve been developing several monitoring methods that can be used to detect and count breeding male bitterns. This year we wanted to measure how well these methods work.
To do this we needed to catch and ‘mark’ as many male bitterns  as possible on Lake Whatuma, in Central Hawke’s Bay. We knew this would be tricky because to-date few bitterns have been caught.  However, as a team we collectively had several years of bird catching experience using a variety of methods…knowledge of two methods that had been used successfully to catch bitterns overseas…an ability to adapt as we went…and a ridiculous amount of dogged determination… And it worked!
Since September we’ve been able to catch six  male bitterns at Lake Whatuma. We caught all six birds by luring them into cage traps using a combination of calls and mirrors.
Playing bittern booming calls within a bird’s territory worked because it tricked the resident male into thinking that a rival male is challenging it. The resident male tries to creep up on this fake rival male intending to see it off. Eventually it sees its own reflection in the back of the cage trap, which it mistakes for the intruding bird, causing it to enter the trap. As soon as the resident male steps on the treadle plate inside the trap, it’s weight releases a catch, dropping the cage door shut, and capturing the bird.
Once caught, we banded each bittern with a metal M-band to make them uniquely identifiable in the hand. 
We also attached the radio transmitters provided by Ducks Unlimited sponsorship to help us locate and  identify the bird even when it was hidden from  us in the thick vegetation.
Before releasing the bird we weighed it, took a range of measurements (such as length of tarsus, bill, wing and tail), and some photos of its bill and feather patterns.
Photos and measurements can be used to crudely determine the health of the bird and as a general guide to help us confirm its age and sex. Each captured bittern was named in the honour of a deceased crooner – so by November we had caught Barry White, Bing Crosby, Tama Tomoana, Prince Tui Teka, Howard Morrison and Elvis Presley.
Once we’d finished processing each captured bird we released them back into their territories.
After that we regularly located birds using the signals emitted from their transmitters. Locations of marked bitterns were plotted to map their territories. We also checked where birds were located during our monitoring sessions and noted if a bird called during monitoring periods, and for those birds that did call we looked to see if observers had succeeded in detecting them. 
The results of our monitoring trial are still being analysed but preliminary results already show that breeding male bitterns have high site fidelity during the breeding season, meaning they always boom from the same area.
This is good news for our monitoring methods as it allows us to assume that booms heard at the same location at different times during the breeding season were produced by the same bird.
There was one exception. Bing Crosby, a bird caught in the northern end of the lake, permanently left his territory in October (midway through the breeding season). However, we have reason to believe that Bing was not as popular with the opposite sex as his namesake – and therefore does not count as a breeding male. Indeed we suspect he left the lake because he was single and  wanted to try his luck at wooing a female  elsewhere. There are several reasons why we suspect this. Firstly, the quality of Bing’s booming, something that’s associated with mate attraction, dropped steadily throughout the breeding season. This was not observed with the other marked males. Secondly, we had fewer observations of unmarked non-booming birds (females?) within Bing’s territory compared to some of the other booming males. This causes us to suspect that any visiting females were not staying for long. 
Thirdly, in the final days leading up to Bings disappearance he became more transient, often appearing in places that seemed well outside of his usual territory.
For example, two days before his disappearance he was found in the heart of his neighbour’s territory cavorting with two unmarked non-booming bitterns. His neighbour was booming within 100 metres of these liaisons - A final desperate attempt at securing a Lake Whatuma female perhaps??
Finally, after Bing’s disappearance we searched his territory for evidence of nest  attempts and were unable to find anything  to suggest he had attempted to mate with a female. We believe he was a single male trying his luck, but still can’t say this with certainty because many of the birds interacting with Bing were still unmarked and the sex of bitterns is difficult to determine from plumage alone.
Still, if we had not had the transmitter on him we would have never known that about these behaviours. Interestingly we observed similar transient behaviours with the other five marked bitterns. Although for them these observations occurred much later in the season and coincided with the time when we were expecting bittern chicks to fledge.
At this time of year (December/January), it makes sense for males to be more mobile, as chicks are supposed  to be relatively independent after fledging,  leaving few reasons for males to invest time and effort in maintaining their territories.
As you can see we still have much to learn about bitterns, their needs and behaviours. However, just in these last six months, through the use of the transmitters provided by Ducks Unlimited, we’ve been able to associate some of our observations with individual birds allowing us to put these observations into greater context.
All six of our marked bitterns have now left Lake Whatuma – again something we did not (and could not) have known would happen if our marked birds were not carrying transmitters.
We plan to continue following these six bitterns over the next six months. Hopefully the more we learn about them, their movements and habitat requirements, the more these observed behaviours will start to make sense.


Published in Issue 163
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