The state’s bird emblem is an indicator species for H5N1, with high visibility populations and low survival rates. Experts are warning of ‘significant mortality’
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When the black swans start dying, Western Australians will know that bird flu has truly arrived.
The birds are an “indicator species” because once they are infected with the H5N1 virus they are more likely to die than survive, according to the University of Queensland virologist Kirsty Short.
“If avian influenza gets into a place where there are black swans … then I think we will see swan mortality and if there’s a significant number of swans, significant mortality.”
WA’s black swans are deeply woven into its identity. As the state’s official bird emblem, the species is emblazoned on buildings, stamps, the flag and the coat of arms.
Now the bird that has come to define the west is facing devastating consequences.
Unlike many birds, black swans lack a key immune protein involved in recognising viral infections, a difference that may leave them vulnerable to a killer inflammatory response.
The species has been ranked as “very high risk” of becoming infected with the virus, according to a commonwealth national risk assessment.
Experts don’t yet know how black swans will respond to living with a virus that, once established, is expected to circulate and evolve in wild bird populations.
Black swans live in both coastal and inland freshwater areas and can form large colonies when breeding. An infected bird could cause an entire colony to die out, the ornithologist Floyd Holmes from Phoenix Environmental Sciences says.
“It is not likely to wipe out all of the swans, but for any local groups of swans, particularly in the south-west, that all congregate and breed in a single place, the potential to just lose that entire population all at once is definitely there,” Holmes says.
“It would be pretty devastating for that local area.”
South Australia, where the virus was first reported, has already reported three mass mortality events involving more than 1,000 greater crested terns. Holmes says the public is also more likely to notice the impacts on black swans because the birds are so large and distinctive.