Backing the bittern: The bird on the brink
Environment Canterbury media release; 14th October 2024
The Australasian bittern/matuku-hūrepo is one of our most fascinating birds, and unfortunately one of our most endangered.
It’s estimated there are only between 30 and 50 bittern remaining in Waitaha/Canterbury, and fewer than 1,000 across the country. They are currently classed as ‘threatened - nationally critical.’
Threats facing the Australasian Bittern (Matuku-hūrepo)
The bittern’s declining numbers are reflective of the region’s shrinking wetlands, where they’re commonly found. Since European settlement, 90 per cent of freshwater and natural wetlands and half of our coastal wetlands in Waitaha have been lost through human impact.
Other threats include collisions with vehicles and starvation caused by:
- changes in water levels that leave birds ‘high and dry’;
- lack of food and/or habitat where the species can hunt; and
- murky water quality (sedimentation) – as bittern are visual feeders.
One of the best ways we can help the species is to protect and enhance our remaining wetlands, and where possible, create new wetlands, to provide an optimum breeding and feeding habitat.
Elusive 'spy' behaviour
If you’ve seen a bittern, consider yourself lucky! They’re known for their cryptic behaviour and are very good at avoiding people. Principal biodiversity advisor Frances Schmechel says bittern have been referred to as the James Bond of the bird world.
“They’re like spies in that they’re very elusive. They kind of skulk around and do a great job at hiding.
“If they are in a situation where they’re startled, they’ll stand upright with their bill pointing skyward and sway.”
The bittern are also known for the “booming” call that the males make during spring.
“It’s such a mystical type of sound to hear in a wetland,” Frances explains. “Some say it’s almost spiritual.”
Listen to the 'booming' sound of a bittern on the Department of Conservation (DOC) website.
Preserving raupō habitat
90 per cent of bittern sightings in Waitaha over the last 15 years have occurred in the Te Waihora and Pegasus Bay areas. Their most important habitat is dense/mature raupō beds on river, wetland or lake edges.
The wetlands around the margin of Te Waihora are the largest remaining area of wetland habitat in lowland Canterbury, covering around 4,500 hectares. A DOC-run willow control programme, which we’re helping fund, is a key initiative for supporting bittern.
Not only do willows suck up large volumes of water but they also encroach on native wetland vegetation such as raupō. They create a dense canopy and interfere with the function of the wetland, including destroying spawning grounds for benthic fish (fish that deposit their spawn on or near the bottom of the sea or lake) – which the bittern feed on.
At Te Waihora, willows were invading the raupō at an alarming rate. The ‘bittern habitat’ aspect was a key driver for establishing and maintaining the control programme, which began in 2011.
DOC biodiversity ranger Allanah Purdie says reversing the spread of willow is a cost-effective and efficient way to support bittern.
“Raupō is by far their preferred habitat - so when you remove the willow, you get bittern.”
As Allanah points out, the species’ perilous future is representative of the overall condition of wetland systems that remain.
“It’s an indicator for all our other wetland species and the health of the ecosystem as a whole, all of which are suffering as a result of long-term wetland degradation.”
Community conservation efforts
In Waimakariri, the Bittern Īnanga Rushland wetland is one of three Kaiapoi projects being undertaken by an extended family who are passionate about restoring biodiversity to the area.
One of the aims is to attract bittern, and the site has also been identified as a potential Canterbury mudfish habitat. It is receiving $15,000 in funding this financial year through the Waimakariri Water Zone Committee.
The support will help with the control of willows and poplars, along with more than 350 metres of fencing to create a large buffer to protect the rushland and make room for plantings.
Landowner Nicky Auld says a bittern is now frequenting the area.
“It was very rewarding seeing a bittern for the first time, and it is now a regular visitor to the rushland - where it feeds on eels, fish and whitebait.
“We’ve been scattering raupō seeds in the hope that the rushland may become even more attractive to these magnificent birds, and a breeding ground.”
Others who have raupō on their property are already in a good position to help. Allanah says wet areas with fresh standing water – about 20 cm deep - are ideal habitat.
“Bittern need areas to take-off and land in, so consider keeping the larger stature plants back at least ten metres from the water, with Carex around the margin and then raupō in the middle.
“The species is intrinsically linked to areas with marginal or dense vegetation. They don’t like being out in the open and are very prone to disturbance. If you have a disturbance event in a wetland they’ll go to ground or disappear.”
Bittern are known for being highly mobile, so when they do disappear – it can be to quite a distance away. One that was fitted with a transmitter was tracked flying from Te Waihora to Blenheim – more than 300km.
The Great Matuku Muster
Another initiative that’s helping raise awareness of the bittern’s plight is The Great Matuku Muster - which calls on people to listen out for, and record, the males’ ‘boom’ sound.
The events take place on one day each month in spring, with the next due on Saturday 19th October and Saturday 16th November 2024 - for up to an hour from sunset.
The muster is supported by a series of workshops around New Zealand to help people learn more about the bird and what to listen for.
Find out more about the Great Matuku Muster, including how to sign up.
This initiative runs alongside annual monitoring by regional councils, DOC and volunteers – aligning with bittern breeding season from October to December.
Our monitoring is getting underway now at key sites on Environment Canterbury managed land – helping build an updated picture of the species’ local population size.
Preventing extinction of the Australasian bittern
Conservationist Peter Langlands, who’s carried out extensive monitoring of bittern in Waitaha, describes the situation as ‘critical’.
“I’m worried that we may lose the source population of bittern in Canterbury. We must act now if we’re to save the species.”
Peter believes a collaborative approach to large scale habitat restoration projects, and scaling up wetland creation, will lead to the best conservation outcomes.
Frances echoes Peter’s sentiment. “They’re such a mysterious, and surprisingly graceful bird. When you see one for the first time – it’s special. It would be really unfair if we didn’t manage to conserve that experience for people.”