A project wants more people to get ‘bittern’ by the matuku hūrepo bug.

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Wendy Ambury calls him Te-rangi, the matuku hūrepo Australasian bittern who lives near her. She will go down to the reeds where he booms. “He suns himself and he just stands there looking at me. And I just stand there looking at him,” she says. She misses him when she’s away.

Ambury’s relationship with Te-rangi is unusual. Matuku hūrepo are typically secretive birds, hiding away in dense raupō reeds. I’ve only ever seen one with my own eyes, despite spending two years working on a New Zealand Geographic feature about them.

They’re large birds, but artfully camouflaged in their wetland homes. You’re more likely to hear a bittern than see it – specifically, the male bittern, who makes a deep whoom call at dusk this time of year. It’s a “magical noise” that Ambury encountered as a child in the wetland near her home. “I would tell my siblings the noise was a swamp monster,” she says.

With wetlands drained and degraded, the bittern’s booms have been dwindling across Aotearoa. The species is now considered “Nationally Critical” – just one step away from extinction. We think there are fewer than 1,000 left, but the population picture is murky.

Ambury hopes that getting New Zealanders tuned in to the bittern’s bassy booms will enable a more accurate estimate of bittern numbers. She has organised the Matuku Muster, a citizen science effort to count as many bittern booms as possible across the country over three springtime evenings.

The first, in mid-September, was hampered by “crud” weather. But the most important boom-count night is coming up on 19 October, when most male bitterns will have settled in a territory and will be booming hard.

By listening all on the same night, you avoid double-counting. Bitterns can be remarkably mobile, flying tens or hundreds of kilometres between wetlands – meaning you can never be sure that my booming bittern isn’t the same as yours, unless we’re listening at the same time.

Taking part in the Matuku Muster is easy. Simply find a good spot on the edge of a wetland (Ambury can help find one near you), pull up a deck chair half an hour before sunset, and record the booms you hear on the app. “If you’re close enough, you can feel it coming through the ground, and you can see the reeds wriggling before the sound actually hits your ears,” she says.

Repeating this survey far and wide and every year will build a more accurate picture of how matuku hūrepo are faring, Ambury hopes. She’s also hoping to get more folks across Aotearoa aware of their plight, and connected with wetlands. Through her Love Bittern project she’s on a “nationwide crusade”, travelling the country in her bittern van to deliver workshops and empower communities to take action.

When she comes home to Ngunguru in Te Tai Tokerau, Te-rangi is waiting. “I first met him when he was at least two years old and then I’ve been with him for five years,” she says. “I can see he’s ageing. His feathers are going ghostly white.”