(NEW YORK) — The vanishing of a rare bird colony in New Zealand has left ornithologists both baffled and concerned for the species’ future, according to experts who spoke to ABC News.

The shore plovers, also known as tūturuatus, left their home, Mana Island, in recent weeks, according to Jess MacKenzie, a spokeswoman for New Zealand’s Department of Conservation.

There were 30 shore plovers on the island at the time. Three of those 30 that left have been recaptured, but the whereabouts of the others is unknown.

MacKenzie suspects they’ve been lost to predators.

“They are extremely susceptible to predation, which is why most predator-free islands are essential and why investment is needed to protect this species,” she said.

MacKenzie said the 30 birds had been transported to Mana Island in February to establish a new colony.

“Unfortunately, over the last few months, they dispersed to the mainland,” MacKenzie said.

She said it was not clear why the birds decided to leave, though many theories abound.

“It could be that a single bird decided to fly to the mainland and everyone else followed them, they may have felt threatened by avian predators or it could be random behavior,” MacKenzie added.

It’s not the first time shore plovers had been transported to the island. In 2007, the birds were introduced to the island, but a rat quickly decimated the population.

“We are very aware of the devastation caused by a single rat to Mana in 2011. … We’ve put a lot of effort into keeping Mana predator free since then,” Mana Island Ranger Nick Fisentzidis said back in February.

Shore plovers are classified as critically threatened in New Zealand, with only about 250 left.

Most of the birds are found on the Chatham Islands, however new habitats are needed because those islands are almost full.

Ornithologists have said that all shore birds, of which there are more than 200 species, are facing great risk.

Dan Ardia, president of the Association of Field Ornithologists, based in Massachusetts, said this is because the birds are migratory and the specific resources they require — whether habitat or food — are under threat for a slew of reasons, including climate change.

“Coastal reclamation, mangral destruction, any kind of dredging” leaves the birds in “enormous trouble,” Ardia said.

While bird populations are declining in general, the Western Hemisphere Shorebird Reserve Network classified shore birds as among those “showing the most dramatic declines.”

The organization said protecting the sites where they rest and refuel during migration is key.

“Loss of any one of these critical staging areas could mean the destruction of a species’ whole flyaway population,” according to the organization’s website.

However, MacKenzie said there is reason for hope.

A population of the birds on Waikawa, on the Portland Island, has proven translocations can work.

The shore plovers were introduced there in 1999, and by 2012 there were 37 breeding pairs. However, a rat incursion killed all but four pairs.

But since then, through “rigorous predator control” the population of shore plovers there has steadily increased, according to the Department of Conservation.

“This is a good example of how well things can go when a colony is finally established,” MacKenzie said. “As long as we can keep predators away.”

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