The chicks choking on a toxic diet of ocean plastic
Lord Howe Island, off the eastern coast of Australia, looks like a tropical paradise. The tiny, World Heritage-listed island is home to just a few hundred people, and is surrounded by white sand beaches and turquoise seas.
But not all of its residents are thriving. A grim reality lies behind the idyllic landscapes: the birds that live on the island are facing death by ocean plastic.
Dr Alex Bond, a bird curator at the Museum, has been documenting threats to the island's bird life since 2009 alongside researchers from the University of Tasmania and Lord Howe Island Museum.
For the last few years, they have been examining the stomachs of wedge-tailed and flesh-footed shearwaters, the most contaminated bird species in the world.
The contents of the birds' digestive tracts are a shocking sight. Alex has found countless pieces of plastic inside them, including balloon clips, pieces of Lego, biro lids, bottle tops and wheels from a toy car.
Shearwater chicks that should be getting a diet of fish and squid are instead being fed meals of plastic by their parents. The plastic pieces have been gathered while the parents are hunting out at sea, and they are leaving no room for real, nutritious food.
The team once found a record 274 pieces of plastic, weighing 64 grams, in one shearwater chick. It amounts to a death sentence for the bird.
Alex says, 'The flesh-footed shearwaters are affected particularly badly, and we don't fully understand why. We are trying to answer that question, as well as measure the impact of ocean plastic on population levels.
'It can be difficult to know whether a bird has been killed as a direct result of ocean plastic because its effects can be insidious. A chick with a stomach full of plastic is clearly going to have a hard time surviving, but there are other threats too.
'Plastic can absorb toxins in the ocean, land in a bird's stomach and release those toxins into the bloodstream - but this isn't an obvious problem to the naked eye. A microbead can pass through a bird's gut, but it leaves a trail of toxins behind.’
Alex has been working with colleagues Dr Jennifer Lavers, an eco-toxicologist from the University of Tasmania, and Ian Hutton, a naturalist and museum curator on Lord Howe Island, as well as a suite of research students.
They have been measuring contaminants in the birds' blood and feathers, as well as studying tissue damage in their liver cells. They can also examine the plastics from inside the birds' stomach, to find out exactly which toxins have been ingested.
Most mornings at work, Alex, Ian and Jennifer find dead or dying birds on Lord Howe's beaches. They take them back to their lab and empty their stomachs - and most are full of plastic.
They also flush the stomachs of living birds when the chicks first emerge from their underground burrows, around 90 days after they hatch, before they make their maiden flight.
Alex says, 'These are chicks that have been accidentally fed all this plastic by their parents. They haven't even fledged the nest yet by the time this amount of rubbish accumulates in their systems, but they will eventually be expected to migrate from Australia to Japan on their own.
'With that amount of material inside them, many will never make it.'
The plastic pieces store up toxic chemicals that can get into a bird's gut and blood, and affect them in other ways. These effects may not be immediately fatal, but scientists are still working to understand exactly how an animal's life can be changed by these toxins.
In a paper published in 2014, Alex, Jennifer and Ian examined shearwater fledglings in eastern Australia. They found that birds with the most plastic in their stomachs were in worse shape, and had higher concentrations of contaminants in their tissues.
It's all taking its toll on the animals, as recent population estimates show the number of flesh-footed shearwaters on Lord Howe has dropped markedly.
However, not all species are suffering as badly. Wedge-tailed shearwaters are neighbours and close relatives of the flesh-footed shearwaters, sharing nesting and feeding sites on Lord Howe Island and in the Tasman Sea.
One of the team's recent papers, published in Marine Pollution Bulletin suggests that while Australian wedge-tailed shearwaters do eat plastic, they eat far less of it than other species, and it doesn't appear to have a significant negative impact on their body sizes.
Alex says, 'Both species eat broadly the same food, breed at roughly the same time of year, and feed in or around the same place, yet one is so much more badly affected than the other, and we have no idea why.'
Seabirds are important indicators of the ocean's wider health because they are at the top of the food chain and because they rely so heavily on healthy marine environments.
For the team working on Lord Howe Island, this is evidence that far more research is needed into the effects of plastic ingestion on animals living in a range of marine habitats.
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You can also join a beach clean-up near you. For UK residents, the Great British Beach Clean takes place from 14 to 17 September. Find out more.
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