Enhanced bird flu surveillance of Australia’s southern coast will focus on the movements of two migratory seabirds species that have tested positive for the deadly virus.
A second bird, a giant petrel, was today confirmed to have a strain of avian influenza known as H5N1 2.3.4.4b, which has killed millions of birds and mammals around the world.
The bird was found washed up near Esperance, WA, after a brown skua that also had the virus was found in the same area on June 14.
Both species spend some of the year on subantarctic islands — with the closest islands known to have bird flu some 4,500 kilometres away — and can winter in waters off Australia from WA to Queensland.
Australia’s chief veterinary officer Beth Cookson said an expert wildlife advisory group had been formed to provide information on the movement and locations of the two seabird species in terms of where they were likely to co-mingle with other animals.
“That will help inform the enhanced surveillance approach that we’ll take to determine whether this is spread further,” she said.
Initially, Australian authorities were concerned the virus would come from the north during the annual migration of migratory shorebirds between September and March.
That is because ducks and migratory shorebirds have been key spreaders of the virus in other parts of the world over long distances.
But the detection of H5N1 on Kerguelen Islands in October 2024, and Heard Island and McDonald Islands in October 2025 indicated spread from the south was another viable route of transmission.
Genomic sequencing is still underway to determine the virus’s route into Australia and whether it came directly from subantarctic islands to the south-west of the country.
How skuas spread bird flu
Ducks and shorebirds were key species in the spread the virus around Europe, Asia, Africa and the Americas since 2020.
But the two species of birds detected with the virus in Australia — brown skua and giant petrel — have been implicated in the spread of bird flu from South America and into the Antarctic region across the Southern Ocean.
Research director Christophe Barbraud, from the marine predator team at the French National Centre for Scientific Research, said that was because of the birds’ feeding habits, ecology and large-scale movements.
“Skuas and giant petrels predate live preys or scavenge on dead carcasses and are thus highly exposed to contamination to bird flu,”
he said.
Birds become infected through the transfer of mucous, saliva, faeces or eating infected carcasses.
Brown skuas are opportunistic scavengers and also steal food from other animals in a habit known as kleptoparasitism. (iNaturalist: Simon Plat, Brown skua, CC BY-NC 4.0)
Marcel Klaassen, an ecologist at Deakin University, said skuas could also get the virus from birds they stole food from.
“When they see a bird has good food, a big crop, they follow them until they throw it up and eat it,” Professor Klaassen said.
Dead skuas have been a common species sampled by researchers throughout the Antarctic region in the past few years.
A brown skua found on an Australian beach was confirmed to be infected with a highly pathogenic strain of avian influenza. (iNaturalist: Oscar Thomas, Brown skua, CC BY-NC 4.0)
During winter skuas and giant petrels that live on subantarctic islands disperse throughout the Indian, Atlantic and Pacific Oceans, including to waters off Australia.
It takes about a month, give or take a week, for a skua to travel from the closest subantarctic islands to Western Australia.
Past studies of skuas that live on Kerguelen Island, near Heard Island, have shown individual birds will fly to offshore areas of Australia all along its southern coastline for the winter.
What is unclear is how long skuas and giant petrels can survive with the virus or how long it takes to incubate in them.
Generally, these migratory seabirds stay offshore when they come near Australia, as they can roost on the water.
“They rarely make it to our shores,” Professor Klaassen said.
“But notably, when they are sick they wash ashore.”
Seabird ecologist Yuna Kim, the seabird project coordinator for Birdlife Australia, said skuas were understudied.
“A lot of penguins get researched because people love penguins, but skuas, because they take penguin chicks, they are not loved by people,” she said.
“But we need to pay attention to these high-risk birds. Their populations are under threat with this disease, and they can transmit this disease to other vulnerable populations.”
How might bird flu spread in Australia?
Professor Klaassen said there was chance the virus had not spread any further than a couple of seabirds.
If we are lucky, a few cases of migratory seabirds with the virus popping up from time to time will be it, he said.
However, given the movements of these migratory seabirds, there are a lot of places around Australia besides WA where that could happen.
While we know little about the full migrations of skuas and petrels, individuals have been spotted by birdwatchers in Australia from the north-west, around the southern coast and up to Queensland.
A giant petrel was found sick with bird flu on Thursday on a beach near Esperance. (Supplied: Lori-Ann Shibish/Esperance Wildlife Hospital and Sanctuary)
Dr Kim said it would be a challenge to monitor the country’s massive southern coastline.
“We have a lot of inaccessible sites. We don’t know exactly what is happening,”
she said.
There were 58 reports to a government hotline of dead or sick birds found in WA on the weekend.
Nine samples have been collected for testing, including one from Esperance.
Dr Cookson said a number of samples from newly reported birds were on their way to a WA lab to be tested.
Dr Kim said if more live birds or carcasses washed up, silver gulls and other scavengers such as eagles and ravens could be exposed to H5N1.
The faeces or dead bodies of infected birds could then spread the disease further, including among sea lion colonies.
Professor Klaassen said seals and sea lions around Esperance might also interact with dead infected birds out of their natural curiosity and playfulness.
Australian sea lions are a common sight around Esperance and may interact with infected birds. (iNaturalist: Tinship, Australian sea lion, CC BY-NC 4.0)
He said it would be bad news if bird flu got into freshwater systems and infected ducks.
Mallards can spread H5N1 after a day of infection and have been found to excrete the virus up to 14 days through their faeces. It quickly spreads through waterfowl populations because these animals both defecate and eat on the water.
Incubation in wild birds of the virus has ranged from a few hours to a week.
Mortality is high in farm birds and a study that used a 2021 sample of the virus found turkeys died within 4.6 days of being infected and chickens within 2.7 days of being infected, in lab conditions.
Australia’s carnivorous mammals, such as possums and quolls, could be exposed to infected carcasses, but it is unclear what impact H5N1 might have on them.
Dogs are highly susceptible, which could be a problem for dingoes.
Feral cats and foxes could be susceptible as both species are on the list of mammals in other countries that have been detected with the virus.
Even if the virus does not get a foothold in Australia this time around, Professor Klaassen warned it was probably inevitable.
The short-tailed shearwater is one of east coast Australia’s most abundant seabirds. (iNaturalist: Vyacheslav Luzanov, Short-tailed shearwater, CC BY-NC 4.0)
So far, the virus has not been detected in East Antarctica, the closest part of the southern continent to Australia, but if it is, there will would be more opportunities for it to jump over.
That is because there would be more bird species that migrate from Australia to East Antarctic waters where they could be exposed, such as short-tailed shearwaters.
“When summer comes here, they move further down south,” Professor Klaassen said.
“There are millions of short-tailed shearwaters. They could form a serious risk in the spread, but I don’t know for sure.”
Short-tailed shearwaters head down to Antarctic waters near Australia in spring. (Supplied: AviFluMap)
Anyone who sees a dead or sick bird is asked not to touch it and report it to the Emergency Animal Disease Hotline on 1800 675 888.
