A distinctive booming sound is returning to the Wairarapa Moana. Most of the surrounding wetlands have been lost after land was drained for farming. Now, after years of rehabilitation work, more of the Australasian Bittern have been heard lately. Country Life heads out at dusk to listen for the matuku-hurepō.

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Kaitiaki of a world-renowned wetland at the bottom of the North Island are excited about the return of a critically endangered bird, the matuku-hūrepo or Australasian Bittern.

Researchers listening for its distinctive booming call around the Wairarapa Moana wetlands say the population has doubled in the past decade - a sign of hope for the lake.

Wander through the Wairarapa wetlands with Country Life

Arrive at dusk on a clear summer evening at Boggy Pond and the skeletal willows in the water are alive with spoonbills, their mullet-style head feathers and wide beaks throwing quirky shapes against the pinkening sky.

Swans float in pairs across the inlet and gulls and terns dive and cackle in the distance.

The bittern is nowhere to be seen this evening but at last count it appears the matuku population is thriving.

Its whare is the raupō - bulrush - flourishing on the lake edge.

Watch out for something like a stick, Sarah-Jane Jensen urges as we make our way through the head-high thicket.

"They quite literally freeze, with their heads in the air, and they look exactly like a stick."

The biodiversity advisor for the Wairarapa Moana Wetland Project has only seen the bird three times here but she's heard it many more.

The birds' deep throated boom is made only by the males.

"I imagine that in the choir they would be the baritone or the bass," Rawiri Smith (Ngāti Kahungunu ki Wairarapa) told Country Life.

He said the matuku is often described as a lonely bird and referred to in waiata (songs).

Smith has been working with his iwi, along with Rangitāne o Wairarapa, the South Wairarapa District Council, the Department of Conservation and Greater Wellington Regional Council to protect and improve the moana under the wetlands project, set up in 2008.

The bittern are among 50 rare and threatened species spotted at the site which is among 2000 Ramsar sites

worldwide.

The Ruamahanga River, part of the network of waterways and lakes forming the moana, was diverted and stopbanked in the 1960s and 70s to ease flooding and allow farming around the lake.

Runoff from surrounding farms, pests and sedimentation are all threats to the habitat but it appears conservation efforts are working…

Go to this episode on rnz.co.nz for more details