What’s this mystery object?

By Karen McGhee, Science and Environment Editor 3 May 2022
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Researchers have been puzzled for more than a decade about an unidentified plastic shape that keeps turning up in the stomachs of seabird chicks on Lord Howe Island.

An international team led by researchers from the University of Tasmania and Natural History Museum (NHM), London, has been working since 2009 on the impact of marine plastic pollution in flesh-footed shearwaters on Lord Howe Island (LHI).

These ocean-going birds migrate annually as adults between their LHI breeding colonies and the Sea of Japan but feed their chicks by foraging in waters off the East Coast of Australia. (see The sorrow of shearwaters)

LHI is in the Tasman Sea, 780km north-east of Sydney, and the shearwater’s annual migration covers about 15,000km return. The species has an estimated lifespan of 30-40 years, meaning that those that manage to survive can cover about a million km during their lifetime.

But fewer and fewer appear to be making it off the island and the reason is thought to be related to plastic pollution.

Related: Birds of Lord Howe Island

Help to survive plastic

For 13 years a team led by Dr Jennifer Lavers, a seabird ecologist at the Institute for Marine and Antarctic Studies at the University of Tasmania, and Dr Alexander Bond, NHM’s Principal Curator of Birds, has been working in LHI’s shearwater colonies to improve the survival of ill and malnourished fledglings full of plastic.

The chicks are inadvertently fed the potentially toxic material by their parents, which collect it from near the ocean’s surface, most likely because they mistake it for fish or squid.

Unidentified plastic objects found in shearwater stomachs on Lord Howe Island. Image credit: Lillian West

When the chicks begin to fledge in late April, just before they attempt leaving the island for their first migration, the research team goes into the colonies each night to gently coax the chicks to discharge plastic that’s accumulated in their stomachs during their first three months of life.

Among the material the chicks bring up is an array of plastics, much of which is faded and broken beyond recognition. But some can clearly be identified, including pen lids, bits of glow sticks from fishing vessels, and tiler spacers used in the building industry.

There are also bits of party balloons and the clips used to tie them as well as pieces of bottle tops.

“And every year, in many fledglings we see, there’s at least one of these very distinctly shaped round mystery items that we’ve never been able to identify,”

Jennifer Lavers says.

“We’ve tried since we began this research to work out exactly what it is, but so far no one has been able to help.

“They’re a bit bigger than a human thumbnail, always a light colour, round shaped and with raised concentric circles. Somebody must know what they are!”

The team recovers up to 10 of these mystery objects every year from the stomachs of flesh-footed shearwater fledglings on LHI. “This strongly suggests they’re commercially or industrially produced and are widespread in the ocean,” Jennifer says. “Otherwise, we wouldn’t find them in so many of the birds.”

Identifying a source

Understanding what the object is could mean it might be possible to identify where it comes from and potentially stop that source of pollution.

Sadly, the research can’t help the hundreds of flesh-footed shearwater fledglings that every year end up dying on the beaches of LHI when they attempt to leave on their first migration, too weak and malnourished to even make it into the air for the first time.

For a full report on this extraordinary research and the impact plastic pollution is having on our oceans, see the July–August issue of Australian Geographic magazine.

Related: 10 magnificent photographs of Lord Howe Island