More than a third of seabirds found dead on New Zealand and Australia’s beaches have plastic in their stomachs.

Auckland Museum curator Matt Rayner worked alongside researchers from the University of Tasmania to autopsy 1700 birds from both countries, and said 37 per cent had eaten plastic.

“I don’t have data on how many died as a result, but certainly there were a number that had ruptured internally, and there had been internal bleeding,” he said.

“It’s not a very pleasant end.”

Because New Zealand has one of the highest biodiversity of seabirds in the world with 85 distinct species, Rayner said we were particularly vulnerable.

The Government is facing mounting pressure to take action on single-use plastics, with roughly three-quarters of city and district mayors signing an open letter calling for a bag levy.

A petition from a group of Wellington school students, calling for the same things, also garnered over 13,000 signatures.

Rayner said the eaten plastics ranged from small, one millimetre pieces to plastic spoons, balloons, and cigarette lighters in larger birds like albatrosses or giant petrels.

“There’s all sorts of crazy stuff.”

Unfortunately, it was often younger seabirds that died from eating plastics, he said.

“An adult albatross can vomit up something it can’t digest, whereas the chick can’t.”

Birds also often became entangled in plastics.

“We’ve had dead birds here with bits of plastic wrapped around their bill, so the bird couldn’t feed.”

It was revealed recently that a third of turtles found dead in New Zealand had also eaten plastic, with plastic bags being the most common culprit.

But unlike turtles, which mistake bags for jellyfish, it is actually the scent created by plastics in the ocean that leads birds to eating it.

“In the marine environment, phytoplankton are eaten by krill and zoo plankton, and when zoo plankton eat phytoplankton it gives off this chemical called dimethyl sulphide.”

“Seabirds have got an amazing [sense of] smell, and they smell dimethyl sulphide in the marine environment. They use that as a cue to feed. They can smell it from kilometres away.”

“The seabirds smell it, and think that’s food, and eat it,” Rayner said.

The toxic effect of plastics on the birdlife was not known, Rayner said.

“The big concern is plastics are now showing up in our food,” he said.

“Scientists have gone to fish markets in South East Asia and Australia, and have purchased fish and shellfish, and found plastics or plastic residues in our food supplies.”

New Zealand’s seabirds go all over the pacific, and as far south as Antarctica. Rayner said they were still picking up plastic debris.

“We are impacting the environment thousand of miles away from where we live.”

Rayner’s work with seabirds has been in conjunction with Tasmanian PHD student Lauren Roman, and The Ornithological Society of New Zealand, who conduct beach patrols, supplying any birds they found dead.

“People can make a difference - 10 million tonnes of plastic going into the sea each year, we can make a difference,” he said.