Tarāpuka have happily settled into Ashburton

The tarāpuka, or black-billed gull, does not exist anywhere else in the world.

“It’s the rarest, and actually smallest of the gull species in the world,” Forest & Bird Ashburton’s Edith Smith said.

And of all the places it could choose to call home, it has chosen Ashburton.

“We’re one of the fortunate districts to have an endemic, endangered bird nesting here - right in the middle of town.”

You can see the river gulls, with their black-tipped wings and dark legs and beaks, settled along the stony ‘islands’ within the Ashburton river when crossing the State Highway One bridge.

Environment Canterbury land management and biodiversity advisory Jess Cochrane emphasises that they aren’t just regular seagulls.

“The red-billed gulls that we think of, at some point in their evolution, diverged. So we’ve got the black-billed gull which has evolved to nest in rivers.

She said there are a few potential reasons the gulls choose to nest on a river underneath a noisy highway.

“They quite like our braided rivers specifically because they have gravel islands in the middle of the river, which means they’re safe from predators. They prefer islands that are weed free for the same reason.”

She said the karoro or black-backed gulls - the seabirds with yellow beaks and black wings - are their main predator, and seem to stay away from the bridge.

“So it offers a bit of ‘natural’ protection [for Tarāpuka].”

A 2017 survey counted that Canterbury hosts around 34 per cent of the entire tarāpuka, with Ashburton occasionally hosting “super colonies’ of 10,000 plus birds.

Cochrane said that populations fluctuate hugely from year to year, with between 3000 and 4000 residing in Ashburton last year.

While that’s a large number for one town, the species is in decline according to the Department of Conservation and Forest & Bird New Zealand.

“People will tend to see them and go, ‘Oh, bloody seagulls, I don’t have to worry about those,’ but they’re definitely worth protecting.”

Smith said heavy rain and flooding were the biggest problems Tarāpuka.

“They’re going to be under threat several times over the season,” she said.

When a braided river floods, nests, eggs and chicks get washed away, and tarāpuka will re-nest or fly to drier shores.

“If a major event startled them, they might just disappear altogether and move out further to the coast.

“There is a plan to create an island a little further downstream [in Ashburton] in the hopes that they will actually go to it.”

But, Smith said, despite river and weather fluctuations, the birds keep coming back to the same rivers every year.

“It’s something inherent in their nature. They’re back in that same spot.”

With the Forest & Bird ‘Bird of the Year’ competition wrapping up this weekend. Smith urges people to get out and vote for Ashburton’s rare, local treasure.

“[Tarāpuka] are still endangered and under threat.”

To vote for your bird of choice, head to birdoftheyear.org.nz and search for “Tarāpuka” or “Black-billed gull”. Voting closes 5pm Sunday.

By Anisha Satya