An Australian bird expert has shed light on how an Antarctic brown skua that died after contracting the highly contagious H5 bird flu ended up on Western Australia’s coast.

On Sunday, June 14, a brown skua was discovered washed up on a beach at the Cape Le Grand National Park, about 700 kilometres south-east of Perth.

It tested positive for the disease on Saturday, and Australia’s Agriculture Minister, Julie Collins, confirmed this is the first time the virus has been detected on the Australian continent.

A giant petrel found nearby was also tested and returned a suspected positive result.

According to BirdLife Australia, both birds tested are thought to have migrated to Australia from the sub-Antarctic, where H5 is already having devastating impacts on the wildlife of Australia’s Heard Island.

Analysis of drone surveys taken on two voyages to the island in October 2025 and January 2026 revealed very high death rates in southern elephant seal pups and increased mortality in king and gentoo penguins.

The brown skua is a sub-Antarctic migratory species that spends most of its life offshore, and while they occasionally visit southern Australia, spotting them in WA is rare.

Birdlife Australia seabird project coordinator Yuna Kim said they are rarely seen along the WA coast, but they can be washed ashore if they are sick or after an extreme weather event.

Dr Kim said she was surprised the diseased skua and petrel were found alive, as after being infected, they are usually not fit enough to leave their colony.

“They probably have been fighting for so long and just unable to fly and floating out at sea, but then with the current they are washed to the beach,” she said.

“When it’s a highly pathogenic, dangerous virus, I would have expected they probably died already.”

Dr Kim said the infected birds were likely from Heard Island or somewhere else in the Antarctic region. Their origin could be confirmed by genetic tests, but due to lots of inaccessible islands, studies could prove difficult.

“It could be somewhere in the Antarctic this bird got the virus, but that could mean that another island might have been exposed to this virus, but we don’t know,” she said.

“They hang out around the fisheries and the fishing vessels. There are thousands of birds just foraging, and it could actually get the disease from there.”

Dr Kim said the brown skua was on authorities’ list of birds identified as a high-risk of spreading H5 due to their migratory, scavenger behaviour.

The brown skua breeds in the harsh environments of the sub-Antarctic and Antarctic zones, where it is well-adapted to the cold and often inhospitable conditions.

While they do sometimes venture into Australian waters during their non-breeding months (March to October), they almost exclusively stay on the open ocean to hunt and feed.

Their movements during breeding season are not as extensive as those of some other migratory species, according to the birdwatching app Birda.

When they are spotted closer to the Australian mainland, it is usually on specialised pelagic bird-watching boat trips far off the coast or washed ashore sick or stranded on remote beaches — such as the case of the brown skua found at Cape Le Grand National Park.

The brown skua’s relative, the south polar skua, was rarely observed around the Bremer Bay area by photographer Martin Cake in early April 2012.

Birda reports skuas have been observed to exhibit intelligent behaviour including the ability to recognise individual humans.

In some cases, they have been known to form bonds with humans who spend extended periods in their Antarctic habitat.

The H5 bird flu strain originated in Asia, but since 2021 has spread across Europe to North and South America and, recently, Antarctica and sub-Antarctic islands, according to a document published by Wildlife Health Australia in January.

Overseas it has infected more than 560 bird species and more than 100 mammalian species, including wild marine and land mammals.