Ducks Unlimited
Tuesday, 27 August 2019 05:00

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
Sunday, 21 July 2019 23:46

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 (http://nzbirdsonline.org.nz/).
 
Species
 
Dabchick
Black Shag
Little Black Shag
Little Shag
White-faced Heron
White Heron
Little Egret
Bittern
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
Total 
 Number 
 counted
38
74
38
15
21
2
1
4
10
2174
1448
128
97
5
1000
42
66
39
136
122
176
11
5647
 

 
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.
 
Species
 
Dabchick 
Black Shag 
Little Black Shag 
Little Shag
Pied Shag
White-faced Heron 
White Heron
Cattle Egret
Bittern
Glossy Ibis 
Royal Spoonbill 
Black Swan 
Canada Goose
Feral Goose
Paradise Shelduck 
Pied Oystercatcher 
Variable Oystercatcher
Pied Stilt 
Banded Dotterel
Black-fronted Dotterel
Wrybill 
Spur-winged Plover
Sharp-tailed Sandpiper
Bar-tailed Godwit
Black-backed Gull
Red-billed gull  
Black-billed Gull
Caspian Tern
Average count 
 1985-1994 
5.1
11.6
3.1 
2 15.0
0
10.5
 0.1
0.1
0
0.5
0
X
X
X
X
14.7
5.6
607.9
187.5
32.3
0.1
57.5
0
0.6
X
0.1
1.5
1.6  
Average count
2011-2014 
52.3 
39.0 
69.3 
15.0
0.3 
12.0 
0.3 
0.0 
1.7 
0.0 
1.7 
692.0 
966.0 
134.0 
24.0 
0.7 
3.0 
516.7 
159.0 
45.0 
0.0 
13.3 
0.3 
0.0 
58.3 
40.7 
195.0 
9.0 
 

 

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 08:18

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
Tuesday, 02 April 2019 08:16

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 08:35

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 04:10

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
Sunday, 25 February 2018 09:06

It’s not all boom and gloom

The fallen leaves crunch below our feet as Kimi, my canine sidekick and I approach the top of yet another hill.

It’s autumn and we’re hunting for Australasian bitterns – but not in the thick raupo or out in the shallow waters along wetland edges as you would expect.

No, we’re on farmland - the last place you would think to look for an endangered bird that is rarer than the kokako.

Yet this is where my telemetry gear tells me we need to go. A loud beep pulses out from the little box that hangs from my neck, and I know from the frequency that Prince Tui Teka is close.

It is hard to imagine Prince in this environment. His streaky dark-brown and beige plumage contrasts markedly against this sea of emerald green - so that instead of blending perfectly into the raupo, as he does in his breeding territory at Lake Whatuma, he stands out like a gangly teenager with stage fright - or worse, a possum in the headlights.

We have long suspected that bitterns forage in farmland drains and small spring fed creeks. After all, this is where members of the public report seeing them. Yet bitterns are also easier to spot in these environments, and the habitat is far removed from what the species is reported to like. This is why these sightings have always seemed like fortuitous interactions rather than something of the norm.

The same can be said for bitterns leaving Lake Whatuma. We always thought it was possible, but somewhat unlikely. In the 1980s, a few bitterns carrying transmitters at Whangamarino wetland in the Waikato left their breeding site and were never re-found. Yet other bitterns marked in the same study were known to remain within the area. There are multiple reasons why we might lose the signal of a transmitter carried by a bittern and not all reasons relate to the bird leaving the area. For one, the thick raupo they live in has a high water content, and therefore dampens the radio-signals emitted by our transmitters. So if one has no idea where a bird has gone, and there’s a chance it is in thick raupo, thorough searches of the area are needed to be sure it has left.

So when the signals of all six of my marked bitterns suddenly disappeared in late December, and thorough searches at Lake Whatuma revealed nothing, I have to admit that I was a little surprised. One or two birds leaving the lake was expected, all of them leaving was not. At the same time it was also logical.

The departure of these birds coincided with a dramatic drop in water levels at Lake Whatuma. For most wetland birds this was a god-send – fish and other small prey items become concentrated in the centre of the lake where several wading birds, like pied stilts, congregate to feed in large numbers. But this is not good for bitterns. Of all the species in the heron family, bitterns are known to be the least behaviourally adaptable.They like what they like and that’s it. They’re not one of those gregarious flighty species that can opportunistically flit between people’s gardens, like the silver-eye. And they are not interested in probing around with yappy pied stilts. They’d much rather stalk and stab their food in peace - preferably somewhere that there’s cover and low water levels. If they can’t do that, they leave.

So they left.

Initially it took us a little while to track them down. Kimi and I spent a lot of time out on the top of hills where it’s easier to get a signal.This is because the angle means there’s less vegetation between us and the bird. I met a lot of farmers and landowners during these quests. Some landowners already knew what a bittern was because they’d flushed them from time to time, and others had no idea -but everyone was equally excited to learn that they have the rarest bittern in the world living on their land. I was overwhelmed by the response of these locals and the appreciation they have of their land and their environment.

Yet finding my birds in these areas also troubled me. Sometimes I would find my bitterns foraging happily on gambusia soup or an army of frogs with lots of cover around them. But more often than not I’d find them wandering along a deep drain looking lost and dispirited. There will have been a time when this happened with brown kiwi. When they were still on peoples doorsteps, being seen by locals who loved and adored them. Yet their habitat was still in decline. They were visible not because they were plentiful, but because they couldn’t find what they needed, and were out and about looking for it…and then one day they were gone.

I believe we’re at this unique position with bitterns. The birds are still around but don’t have everything they need for the population to increase. This is a concern because there will be multiple factors driving the decline of bitterns and many of these factors are still poorly understood. The longer a species remains endangered the harder it is to reverse the decline. If you need any more evidence to convince you of this, you only have to look at how intensive (and expensive) the kakapo recovery program is – a species that is currently only one threat classification rarer than bitterns.

The signal emitted from the transmitter carried by Prince Tui Teka gets stronger and suddenly he flies up out of a tiny raupo patch at the edge of a stream. I know that he saw us long before we saw him. As soon as we came over the brow of the hill he will have been tracking us – just as we were tracking him. He will have been standing in the raupo with his beak pointing towards the sky and only his eyes moving as he watched us across the paddock. He will have seen us pause several times to visually scan the raupo patch. The same patch he was hiding in. Who knows he may have seen us look right at him. Yet until this moment we had not spotted him, and even if we had his plumage makes him look exactly like all of the other raupo stems in the same patch.

He has only flushed now because he knows the game is up.Thanks to the transmitter he carries his camouflage no longer prevents us from re-finding him. I watch him land further down the stream before placing my boot in the water where he was previously standing – the stream is shallow and several small fish and amphibians dart away from me and disappear into the aquatic vegetation. This is one of the better places I’ve found him. There is some cover for him so that he can hide while he forages and the water is clear and shallow enough for him to see his prey. I leave him in peace and head off to find the landowner and congratulate them on this discovery. It’s not all boom and gloom – this landowner likes bitterns and has already said he will not remove any of the habitat Prince uses. 

I still suspect Prince doesn’t have everything he needs but at least this site is better than the empty drain he was wandering along last week.Upon returning to my van on the top of the hill I have a quick listen for the bittern Tama Tomoana with my tracking gear. Members of the local hapu named this bittern after one of the grandsons of Henare Tomoana, a prominent Maori leader in the Hawke’s Bay region in the late 1800s. 
Tama’s father, Paraire Tomoana, composed a number of well known waiata including ‘Po Karekare Ana’. Tama himself was renowned for his rich baritone booming voice – just like our Tama. (And the leadership and musical genes were passed on to Tama’s son, Ngahiwi, who currently chairs Ngati Kahungunu Iwi Inc.). Yet it’s been a while since we’ve heard anything from Tama the bird.

Tama has been missing for seven months now. During the breeding season he was one of our most site-loyal birds and he was regularly found booming within a small area of less than 2 hectares in size - basically one small raupo patch. This was in contrast to some of the other bitterns, like Barry White, who boomed from lots of locations within a 15 hectare area.

This previous site-loyalty left us extra surprised when Tama disappeared and then could not be found. By now all of the other bitterns were accounted for – even Bing Crosby, who had originally flummoxed us last year by disappearing mid-way through the bittern breeding season. In late January we happily rediscovered Bing at Wanstead swamp, a site that’s about 15 kms from his breeding site. Of all of our wandering bittern, Bing was found the farthest from home. We looked for Tama in all of these areas too and nothing was heard.

Colleagues in Australia had recently attached a satellite transmitter to a juvenile male bittern and found that this bird moved farther than 550 kms after breeding had finished, crossing two state borders. Clearly our bitterns could physically move long distances if they want to - this got us thinking that perhaps Tama has done something similar? Five months after he went missing we decided we needed to broaden our search, so we put out a national plea asking anyone with access to telemetry gear to check their wetlands and listen for his signal. People looked for him at wetlands across the country - from Northland down to Waituna lagoon in Southland. His signal was still not found.

In June, all five of our autumn wanderers came back to Lake Whatuma. We waited with baited breath to see if Tama would also return - but his signal remained silent. By July 28, local landowner Max Lyver reported hearing the first bittern boom on the lake. The breeding season had begun, but still Tama was missing. We’d given up hope. Then on August 12, eight months after he’d left the lake, and over one month later than all the other marked male bitterns, Tama’s signal was once again heard beeping from his usual breeding territory. He was back and booming again. Where he went we will never know. He clearly still has a story to tell. This year we hope to recapture him so that we can replace his radio transmitter with a satellite transmitter - kindly donated by Ducks Unlimited, NZ. This will allow us to track him regardless of where he goes, meaning we will be able to get a complete story of his autumn adventures next year.

To me, Tama’s return to Lake Whatuma highlights just how much we’ve learned about the habits and behaviours of these birds over the 12 months they have been carrying transmitters – and yet how many mysteries still remain.

Without Ducks Unlimited, NZ’s continued financial support of this project we would not have been able to unlock these bittern secrets. Knowledge gained by this project is being used to help inform bittern conservation projects nationally.

Emma Williams
Published in Issue 165
Sunday, 25 February 2018 07:47

Australasian bittern/matuku

Bitterns are found throughout New Zealand - in the North Island they predominantly inhabit Northland, Waikato and East Coast wetlands; while in the South Island they mostly inhabit West Coast, Canterbury and Southland wetlands. The most important bittern site nationally is Whangamarino Wetland, a large and diverse wetland complex in the Waikato.

Bitterns are large, stocky birds, with streaky dark brown and beige plumage on their throat, breast, abdomen and thighs; and dark brown on the neck and back. The head is dark except for pale beige around the cheek, forming a pale eyebrow. Plumage can vary significantly and may be age related.

Bitterns are rarely sighted due to their exceptionally cryptic behaviour, inconspicuous plumage resulting in excellent camouflage and the inaccessibility of many wetlands. They are mostly active at dawn, dusk and throughout the night. Bitterns are occasionally spotted in the open along wetland edges, drains, flooded farmland and roadsides.

They are very sensitive to disturbance and will silently creep away to avoid detection, or adopt the infamous ‘freeze’ stance (with the bill pointing skyward) if approached. This allows bitterns to blend into many environments, whilst maintaining a close watch of surroundings. If an observer continues to advance on a bittern, then it will eventually take flight in a laborious manner.

Often the only sign of bittern presence in a wetland is the male’s distinctive booming call at the beginning of the breeding season. Each call sequence may consist of 1-10 individual booms, with an average of 3 booms. Boom sequences are repeated at regular intervals, and normally preceded with inhalations or gasps. Females are mostly silent, apart from producing an occasional ‘bubbling’ sound upon return to the nest, or a nasal ‘kau’ when alarmed. Bitterns in flight may produce a resonant ‘kau’ or ‘kau kau’.

The breeding season is extremely long, spread over a 10-month period. Females construct a reed platform nest amongst dense vegetation deep within wetlands.

A clutch of 3-6 eggs is produced between August and December (peaking in November), and then incubated solely by the female for 25 days. Chicks remain in the nest for 7 weeks and fledge from November to May. Bitterns are considered an indicator of wetland health, as they are dependent on the presence of high quality and ecologically diverse habitats, which are rich in food supplies (such as eels, fish, freshwater crayfish, aquatic insects, molluscs, worms, spiders, frogs and lizards).

Bittern numbers have declined drastically since the arrival of European settlers, with over 90 percent of freshwater wetlands now drained and cleared. Ongoing wetland degradation continues to be the chief threat, resulting in habitat modification and loss, reduced food availability and poor water quality. Other threats contributing to bittern declines include predation by introduced mammals (particularly cats, rats, dogs and mustelids), human disturbance of nesting bitterns, as well as power-line and vehicle collisions.

You can help bitterns by becoming involved in wetland conservation and reporting all sightings (or calls) to your local Department of Conservation office. Most importantly you can protect wetlands on your property by planting native vegitation to create riparian buffers and fencing waterways from livestock.

Sabrina Luecht
Wildlife Project Administrator
(supplied by The Isaac Conservation and Wildlife Trust)

Published in Issue 165
Thursday, 22 February 2018 07:50

Urban bittern chicks

Urban bittern chicks get into strife

Now, if I was to ask how many of you have seen a juvenile bittern or a bittern nest, I think it’d be safe to assume that most of you haven’t. And that’s saying a lot given that you are all wetland enthusiasts who regularly work and play in these kind of habitats.

So when we got a report that a female bittern chick had been found wandering along a road in Christchurch you can imagine our surprise. What was one of the most cryptic and secretive  wetland birds doing on a road in the city? And the surprises didn’t end there – a few weeks later a second female bittern chick walked into a residential garage, only 500m from the location where the first bittern was found. 

There had to be a nest nearby – but where?

Both bitterns were very skinny and clearly  dehydrated. They were taken to bird rehabilitator Jackie Stevenson, who set about trying to fatten them up and get them feeding for themselves. In the meantime, local  ornithologist Peter Langlands set about trying  to find their nest.

Now this is no easy task. Bittern nests are  tricky to find. A broody female bittern will build her nest by bending blades of raupo to form a floating platform that is perfectly  hidden in the thick vegetation. And she’s not necessarily alone. Male bitterns can have  multiple females, which all appear to nest within close proximity to each other.

Once a mother-to-be is happy with her nest she’ll lay between 3 and 5 eggs before starting to incubate. She hatches the eggs and rears the chicks alone, apparently chasing the male away if he tries to get too close. While incubating, she’s almost impossible to see as her streaked plumage blends perfectly in  with the surrounding vegetation. Occasionally she’ll slip silently off the nest to feed, but only momentarily as this leaves her eggs vulnerable to predators. 

After about 25 days, her eggs will hatch to produce little fluffy chicks with Albert Einstein inspired hairdo’s. These fuzz balls, emerge as masters of disguise straight from the eggs, and will adopt a perfect ‘freeze pose’ that looks similar to that of the adults if they are disturbed. Chicks fledge at about seven weeks old. However, there is some suggestion that they may start wandering from the nest as early as two weeks old - which is perhaps how one chick ended up on a city road and the other in a household garage.

Midway between the locations where these two birds were found lies Travis wetland, a 120 hectare swamp complex that has been  restored over the last 15 years by the Travis wetland trust and the Christchurch council.  It is the most likely place where these two birds came from. As it happens Travis is a noteworthy place, with an interesting history. In the 1960’s, this beautiful wetland was under threat from developers, who wanted to convert it to a residential area. Luckily, the locals had other ideas. They realised the importance of the site’s natural biodiversity, and argued long and hard for its protection. After a long battle that involved a petition signed by almost 7000  people, biodiversity won out, and in 1997 the site became a natural heritage park. 

And lucky for bitterns that it did!

Since then, these two bitterns have done well in  captivity and we were able to release them over the festive season - one along the Waimakariri river and the other at Harts Creeks. We attached radio transmitters to both bitterns, one of which was kindly funded by Ducks Unlimited. Both of these birds will be tracked regularly by local enthusiasts and, as female  survival and breeding success is the secret to  saving a species in decline, and these birds are the only females to carry transmitters at the moment - the information we gain will be essential for saving the species. 

Emma Williams

And thanks to Gill Lundie for organising the school visit. 

Published in Issue 167
Friday, 16 February 2018 08:18

Project Bittern (Matuku) Report

Ducks Unlimited NZ AGM (23 July 2016)

Emma Williams has continued working on the bittern project assisted by me and other volunteers. 

Key points are:

  1. Emma graduated with her Doctorate  Degree at Massey University which was based on bittern research. A huge thank you to DU for helping fund a major part of her work to learn more about this iconic critically threatened species.
  2. A total of 10 male bitterns (six 2014 and four 2015) were captured at Lake Whatuma and transmitters attached. Of these 10 birds, nine left the lake over summer with one bird remaining on the lake. The bird that remained on the lake was found dead in late April in raupo and cause of death unknown. Four of the birds have returned to the lake in July and one other is being monitored at a  wetland 10kms away. In spite of extensive  searching the location of the remaining four birds is unknown, but it is most likely they will return to the lake in time for spring like birds did last year. The DU funded transmitters have contributed significantly to our much increased knowledge of this secretive bird.
  3. Emma travelled to Christchurch earlier this year to place transmitters on two bittern chicks that had been found abandoned not far from Travis wetland on the outskirts of Christchurch. These have been monitored by local people. One bird is still alive near the mouth of the Waimakariri River north of Christchurch and the other was found dead in mid May near the mouth of the Opihi River over 100kms south of Christchurch. This bird was examined and appeared to have died of starvation which is not uncommon overseas with bittern. Very interesting results plotting the movement of this juvenile bird and proves that bittern can move considerable distances.
  4. We held a very successful meeting on April 6 for the local Waipukurau community, landowners and Iwi to up-date them on the bittern project. Over 50 people attended and DU received well deserved acknowledgment for their significant contribution to the project.
  5. Emma has done no further school talks in the Wairarapa but will complete others this spring organised jointly between her and Gill Lundie. She has spoken to a number of schools in Hawke’s Bay. Emma continues to provide written articles for Flight.
  6. Bittern are a species under severe threat from wetland loss, predation, poor food supply and human disturbance. Population trends are negative. The Department of Conservation operate a conservation threat classification system of bittern and last month bittern were upgraded to the highest level of Nationally Critical Threatened Species. Kakapo and takahe  share the same ranking which highlights  the plight of this iconic wetland bird.
  7. It is important that DU continue to support  the bittern conservation programme and encourage others (DOC, Forest & Bird) to commit to the preparation of a national bittern recovery plan.
  8. In 2015 DU Directors agreed to support the bittern project to the level of $25,000 to enable Emma Williams to continue her research work and purchase transmitters. Expenditure to date is (Emma Williams $7322) and (transmitters $9211.25). The remaining $8467 will be utilised this coming spring/summer.

John Cheyne

Coordinator Project Bittern (Matuku)

Published in Issue 168
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