Flesh-footed shearwaters: The chicks choking on a toxic diet of ocean plastic

Shearwater chicks that should be getting a diet of fish and squid are instead accidentally fed meals of plastic by their parents.

“The chicks are in their burrows for 90 days,” says Alex. ‘The parents lay one egg a year and that hatches in late January. The parents then spend the next three months going out into the Tasman Sea, collecting food or plastic, bringing it back and feeding the chick.”

The team once found a record 64 grams of plastic, made up of 274 pieces, in one shearwater chick. In another in 2023, they counted a staggering 405 pieces of plastic. 

Plastic can account for 5–10% of the chick’s total bodyweight and all that material leaves no room for real, nutritious food. It amounts to a death sentence for the bird.

“The flesh-footed shearwaters are affected particularly badly, and we don’t fully understand why,” says Alex.

Health checks for shearwater chicks

Alex has been working with colleagues Dr Jennifer Lavers, an eco-toxicologist from the Esperance Tjaltjraak Native Title Aboriginal Corporation and Dr Jack Rivers Auty from the University of Tasmania. They’re also joined by a suite of research students.

The team have been measuring contaminants in the birds’ blood and feathers, as well as studying tissue damage in their internal organs. They can also examine the plastics from inside the birds’ stomach, to find out exactly which toxins have been ingested.

Most mornings when they’re working, Alex, Jack and Jennifer find dead or dying birds on Lord Howe Island’s beaches.

After 90 days in their underground burrow, the little birds fledge and head for the water. Those too weak to face the ocean can be rolled by the waves and drowned. 

The scientists take the birds back to their lab and empty their stomachs - and most are full of plastic. The researchers also flush the stomachs of living birds. They do this when the chicks first emerge from their underground burrows, before they make their maiden flight.

They use a technique called lavage. Seawater is gently pumped into a chick’s stomach. The bird coughs it back up and into a bucket. Anything they’ve eaten that’s lodged in their belly comes back up with 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 working to understand exactly how these toxins can change an animal’s life.

In a paper published in 2014, the team examined shearwater fledglings in eastern Australia. They found that birds with the most plastic in their stomachs were in worse shape. They also had higher concentrations of contaminants in their tissues.

“Their stomachs are fantastic organs,” says Alex. “They have all these little folds in them, which basically serve to increase the surface area of the stomach so that the stomach wall can absorb all the nutrients the birds should normally be eating.”

“But when you get plastics in there, you get an inflammatory response.”

In 2023, Alex and his colleagues named this new disease ‘plasticosis’.

The action of plastic repeatedly digging into the bird’s stomach wall causes irritation. As it happens over and over again, it can cause excessive amounts of scar tissue to form. Ultimately, this reduces the flexibility of the stomach tissues and causes their structure to change.

It’s all taking its toll on the seabirds. Recent population estimates show the number of flesh-footed shearwaters on Lord Howe Island has dropped markedly.

Is plastic affecting all Lord Howe Island’s seabirds?

Not all species are suffering quite as badly.

Wedge-tailed shearwaters are neighbours and close relatives of the flesh-footed shearwaters. They share nesting and feeding sites on Lord Howe Island and in the Tasman Sea.

One of the team’s papers finds that while Australian wedge-tailed shearwaters do eat plastic, they eat far less of it than other species. It also doesn’t appear to have a significant negative impact on their body size.

“Both species eat broadly the same food, breed at roughly the same time of year and feed in or around the same place,” explains Alex. “Yet one is so much more badly affected than the other, and we have no idea why.”

Hear Alex talk about his work and explore more about what our plastic addiction means for the planet in episode four of our podcast.

Why do we need to keep studying birds?

Seabirds are at the top of the food chain and rely heavily on healthy marine environments. This makes them important indicators of the ocean’s wider health.

The work of the team on Lord Howe Island proves that we need far more research into the effects of plastic ingestion on animals living in a range of marine habitats.

How you can help

Reduce your plastic footprint by cutting down on single-use plastics like water bottles and coffee cups.

Be mindful of where your plastic waste is ending up. Try to recycle plastic where facilities are available.

Report birds tangled in plastic or other debris to help scientists understand more about the scale and spread of plastic pollution.

You can also join a beach clean-up near you. For UK residents, the Great British Beach Clean takes place each September. 

Find out more

Unravel the epic story of birds, from surviving a mass extinction event to inhabiting every continent on Earth, at our new exhibition Birds: Brilliant and Bizarre. 

Discover the secrets to birds' success and their surprising and often shocking tactics for survival. Exhibition opens 24 May.  Book your tickets.