Protecting the bittern

Emma Williams with bittern chick, photo courtesy of Anita Spencer.

Emma Williams with bittern chick, photo courtesy of Anita Spencer.

In an attempt to protect one of New Zealand’s rarest and most secretive birds the Department of Conservation is running a bittern conservation programme. With the assistance of Environment Canterbury biodiversity funding the programme aims to help the Department of Conservation learn more about the Australasian bittern and increase the population.

Anita Spencer, Biodiversity Ranger, Department of Conservation, says within Canterbury Te Waihora is a very important site for the bittern and is essential for ensuring their overall survival.

The bittern, only found in New Zealand, Australia and New Caledonia, are ranked as nationally endangered by the Department of Conservation.

“We estimate that the population of the bittern in New Zealand is about 1000 but because the birds are so elusive it’s really hard to get an accurate picture,” says Anita.

Example of a predator trap, photo courtesy of Anita Spencer.

Example of a predator trap, photo courtesy of Anita Spencer.

“To try and protect the bittern, particularly when nesting, a predator trap line has been set up at Harts Creek,” she says.

“The bittern needs active management because like many New Zealand birds when threatened bittern freeze and rely on their camouflage to avoid danger . This technique was fine in pre-human New Zealand when the predator was Haast’s eagle/Pouakai hunting by sight, but now that the bittern faces predators like cats and stoats which also hunt by smell, hiding and not moving makes them a very easy target,” she says.

The Department of Conservation undertake monitoring in spring each year by contracting ornithologist Peter Langlands to go on site for 3 nights at dusk to count the number of booming males. This is done in spring because at this time of year the distinctive booms of territorial males can be heard.

“While only males boom, this gives us an idea of the population,” she says.

The Department of Conservation also has monitoring sites at three other wet lands around the edge of Te Waihora.

To assist the Department of Conservation in further understanding the bittern, two bittern chicks had transmitters placed on them in December.

One of these chicks was released at Harts Creek and it was only the second time a female bittern has had a transmitter placed on them.

“Having trackers on the bitterns provide us with a real opportunity to try and learn more about these cryptic birds,” says Anita.

“Even though the transmitters are in place it has been hard to track the bittern at Harts Creek because they are so well camouflaged. We could be within a meter of her and still not see her,” she says.

The Department of Conservation are also considering adding a research component to their work so that they can learn more about the local population of the Australasian bittern, particularly regarding nesting success and seasonal movements of adults.