Covid 19 coronavirus: Fears for New Zealand's endangered native seabirds during lockdown

Conservationists fear feral cats could be mowing through the country's highly-vulnerable seabird populations with trapping projects halted during the lockdown period.

While the four-week lockdown has heavily reduced air pollution and seen some urban areas revert to nature with birds flourishing, the reality is because of introduced predators much of the wild populations rely on human intervention for survival.

The majority of New Zealand's native land birds had well and truly finished their breeding season before lockdown with chicks having left their nests - the most vulnerable stage.

But many seabird species take slightly longer, and spend from around late March to May alone, fledging in their burrows, while their parents are out at sea collecting food.

At level 4 nearly all trapping and monitoring work was halted, and at level 3 only some projects have been able to resume.

Tītī, also known as muttonbird or sooty shearwater. Photo / File

Black petrels, tāiko, were once found all across the North Island but were driven out of the mainland by feral cats, pigs and rats.

Today they breed in only two places: Little Barrier Island/Hauturu and Great Barrier Island/Aotea.

While on predator-free Hauturu the breeding season is relatively safe, next door on the larger Aotea the major threats to the chicks come in the form of feral cats, and to a lesser degree wild pigs.

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Wildlife Management International senior ecologist Biz Bell said the colony around Mt Hobson/Hirakimata had about 2700 breeding pairs. With about a 70 per cent success rate she estimated there could be about 2000 chicks in their burrows at present.

While in their burrows the chicks were safe, but at night they would go outside to practise flapping their wings and to develop their muscles, along with getting rid of their down and converting it to feathers.

But stopping them gaining that valuable experience is a population of feral cats.

Generally, it is kept relatively low by trapping down in the Okiwi basin, but cats can roam 10-15km in a night so it does not take many to wreak havoc, and they are also rather cunning.

"They learn the behaviour of the chicks, and know to wait outside the burrows for them," Bell said.

"If trapping is maintained they can be OK, but now is a critical time."

A black petrel, which breeds once a year on either Little Barrier Island or Great Barrier Island, before spending the rest of its time off the coast of Ecuador. Photo / File

The Department of Conservation had been trapping up until the lockdown but has had to pause ever since along with Bell's monitoring work, leaving the fate of the birds unknown.

"We are always concerned, every one of these birds is very important."

Tāiko generally live 40 to 50 years, and breed just once a year, producing just one chick.

The remains of a black petral that had been killed by a feral cat. Photo / Supplied

After fledging in early May they head off on a great OE to the pelagic waters off the coast of Ecuador, spending a couple of years at sea before returning to New Zealand. They don't start breeding until about age 6.

They are classed as nationally vulnerable, with a population slowly declining. Their biggest threats off land are fishing vessels and sea temperature changes.

Meanwhile down south, Forest & Bird Otago Southland regional manager Sue Maturin, who looks after a tītī or sooty shearwater colony on the Otago peninsula, said there were "grave fears" for the seabirds during the lockdown.

A black petrel burrow that had been damaged by a wild pig on Great Barrier Island. Photo / Ed Marshall

Like the tāiko, tītī have a similar fledging window and are also vulnerable to feral cats.

"This time of year they are big fat plump chicks left all alone - they are very vulnerable."

Maturin said they'd gained permission under level 3 to continue their work and so on Tuesday raced out to check on the colony.

To their amazement, they only found several dead chicks and a dead adult. There were "plenty of signs of cats and possums" and many abandoned burrows, but far less damage than expected.

Forest & Bird volunteer Graeme Loh with a dead chick at the Sandfly Bay colony on the Otago Peninsula last year. Photo / Sue Maturin

The previous year all 13 of their monitored burrows were predated. This year 10 remained intact.

"It is hard to say what was behind that, but we were doing intense trapping before lockdown. We might have kept them just low enough."

Feral cats are caught live, and need to be checked every day, meaning no traps were active over the lockdown.

Forest & Bird central North Island regional manager Rebecca Stirnemann said the fate of these seabirds highlighted how they needed protection.

"We have seen a lot on social media saying nature has been doing really well under lockdown, but in reality, a lot of New Zealand's nature needs our help.

"It is very scary if we even lose just one of these birds. We just hope as soon as it is safe people can get back out there and do the work that needs to be done."

A fat chick at the St Clair cliffs colony inside a predator proof fence last year. Photo / Sue Maturin

A Department of Conservation spokesman said only limited predator control work continued under lockdown, including staff living and working on conservation islands where it was critical to maintain island biosecurity and protect the rare and endangered wildlife.

This included for the critically endangered Chatham Island tāiko, with just 25 chicks this season, as the team doing the pest control and monitoring were already in an isolated bubble.

Its relative the black petrel on Aotea was less critical, with the species area widely spread across the tops of the island, he said.

Control of feral cats to protect the pāteke population down at the coast normally kept cat numbers under control.

Level 3 would see some more DoC field work resume, but community trapping groups should not check traplines on public conservation land or other public land without approval, he said.

"Any groups checking traps will need to show how they can carry out this activity safely, following public health guidelines to prevent the spread of Covid-19."

• Covid19.govt.nz: The Government's official Covid-19 advisory website