Joining forces to protect the bittern

Environment Canterbury has committed to continue working with the Department of Conservation and local landowners to protect bittern/matuku habitats.

The Australasian bittern is an endangered wetland bird, found only in New Zealand, Australia and New Caledonia. The big, beautiful birds are hard to see, but they can be heard. They face predators like cats and stoats. When they are under threat from a predator, they freeze and rely on their camouflage – but this makes them an easy target for predators that hunt by smell.

Department of Conservation biodiversity ranger Allanah Purdie says it is thought there are fewer than 1000 bittern left in New Zealand and that number is continuing to decline.

“The most dramatic reduction in population has occurred in the past 50 years. The bittern was recently classified as critically endangered, and if trends continue it will decline into oblivion,” she says. 

Protecting bittern habitat 

Environment Canterbury Regional Support Manager Dirk Brand says the regional council’s role is to protect the wetlands, lowland streams and estuaries the birds live in, so they can thrive.

“Habitat loss is the single biggest threat to bittern populations in Canterbury, so that’s why we’re working on this project to better understand and manage bittern habitats,” says Brand.   

Work carried out in partnership with the Department of Conservation and willing landowners has been taking place around Te Waihora/Lake Ellesmere, at the mouth of the Waimakariri River and at other wetlands around Canterbury.

“The stronghold of our bittern population is around Te Waihora, so our work so far has included predator control, tracking and monitoring the birds, surveys, and habitat protection, enhancement and creation,” says Brand.  

Bittern thrive in healthy wetland ecosystems like estuaries, hāpua, coastal lagoons, lowland streams, and wetlands.  They prefer raupō and clear shallow water with good visibility that has wetland vegetation nearby.  They are happy on farms with good habitat as well as more remote areas.

Recently two juvenile birds from Travis Wetland were found starving and kept until healthy, then released. Unfortunately, over winter, one travelled south to look for food in wetlands, coastal areas and lowland streams but eventually died of starvation near Temuka.

“That highlights how important the health of ecosystems like wetlands are for our indigenous biodiversity including the bittern, and that a network of them is required to protect this wide-ranging bird,” says Brand.

Using VHF transmitters to tag bittern

Four birds were caught and tagged with VHF transmitters last spring and at the end of the breeding season all of them moved out of these wetlands and couldn’t be found despite rangers checking for them over large areas.

All four birds have reappeared again in the last month and it is largely a mystery where they have been for most of the year. This spring the team is hoping to attach satellite tags to the birds to help crack the mystery of where these birds are travelling to.

New Zealand bittern with transmitter

A bittern ready to be released with a transmitter. Photo supplied by Department of Conservation.

Progress expected in coming years 

“While we have not yet seen an improvement in the population of bittern as a result of this project, we are starting to gain a better understanding of these elusive birds. Both the Department of Conservation and Environment Canterbury have committed to continue putting time and money into this critical project, and we are expecting to see the results of the groundwork that has been laid in coming years,” says Brand.   

“This is a good example of how we can protect our region’s indigenous biodiversity by working together with other agencies and with our communities,” he says.