Hawke's Bay does not have the largest population of the birds in New Zealand, but research conducted in the region means its population is the most understood, and there is an extensive push to save them.
That push is led by retired volunteers John Cheyne and Rook Hans, alongside the Department of Conservation and an army of volunteers.
"We know more about the regional population of bittern in Hawke's Bay than any other region in New Zealand," Cheyne said.
"So we're in a much better position now to try to identify what conservation initiatives we need to implement and action."
Cheyne has managed to stabilise the Whaatuma population in Central Hawke's Bay, and at the top of the Ahuriri Estuary Hans has gone one step further.
He is managing what is thought to be the only population in New Zealand where bird numbers are increasing.
Cheyne said loss of habitat is a key reason for the dramatic decline in bittern population.
James Mackie checking one of his predator traps. Photo / Laura Wiltshire
"We've lost, in Hawke's Bay, 98 per cent of freshwater wetlands. Across New Zealand that's about 90 per cent.
"They need a home to live in and when the freshwater wetlands are gone, that has a huge impact."
There is also the impact of mammalian predators, with female bittern particularly susceptible to predation while nesting.
It means the first step in stabilising the bittern population tends to be predator control.
At Whaatuma, one of the people taking care of that is local farmer James Mackie.
Along with his team he traps feral cats, stoats, ferrets, weasels, hedgehogs, rats and mice.
"They go for the eggs, go for the nest, and they chase whatever else."
He said the bittern had brought together a diverse group of people, everyone from hunters, who started the push in Hawke's Bay, to anti-hunting groups.
"Everyone is all on the same page now, because everyone actually has the same goal."
Mackie grew up in the area, and said over the past few years, there has been a noticeable increase in bird life across the wetlands.
Meanwhile, in Ahuriri, Hans has taken a two-step approach to managing the population.
"Predators is one thing, but if you've only got 1.9 per cent of your wetlands left, you need to fire two barrels," Hans said.
"So what we were doing was doing the predator control, but we were building habitat for the young birds which were produced to go into."
A before and after shot of the wetland creation done by Rook Hans. Photo / Laura Wiltshire
He said after they flooded the first section of land, a pair turned up.
"And they've been nicely making me little babies ever since.
"So I thought, no bugger it, I'll try it again.
"So we moved downstream, below that, into what is called block two, and we did the same thing.
"We flooded that and boom, we got another one and his wife, and they've been making me babies too."
DoC senior biodiversity ranger Denise Fastier joked that Hans was attempting to "take over the world" with his project, and Cheyne said the habitat work was making a world of difference.
"We can improve the habitat in places, but there are quite limited opportunities, regionally and nationally, they are just sort of specific sites," Cheyne said
"But if we can get water back in there and manage it right, along with the predator control, locally on those sites you can actually make some real progress."
Bittern are now breeding in the Hawke's Bay Regional Council-created Horseshoe wetland at the Waitangi Estuary.
In the Wairarapa, Ducks Unlimited have created a 60ha wetland, similar to what Hans has done but on a larger scale.
Cheyne said bittern are not breeding in there yet because the wetland is still maturing, but he imagined they would see birds in the next year or two.
"Hawke's Bay is a template for the rest of the country for bittern."
