The highly pathogenic H5 bird flu that has killed millions of wild birds globally since 2021 has arrived in Australia, and the country's native species — encountering the virus for the first time — face an asymmetric threat. The federal government announced its first vaccination plans for captive native birds last week. Victoria moved to vaccinate wild little penguins on Phillip Island after detections in terns, and on Saturday confirmed the first death of a little penguin from H5 — a species milestone nobody wanted. The government's risk assessment of every Australian bird and mammal species identifies the silver gull as "high risk." Prof Richard Kingsford, director of the Centre for Ecosystem Science at the University of NSW, calls seagulls the species most likely to bring bird flu home to the Australian public. Gulls are highly mobile scavengers found in flocks across cities, wetlands, and inland areas — a near-perfect transmission profile. First cases in South Australian seagulls appeared in late July. Raptors face a parallel threat. The white-bellied sea eagle occupies a "similar niche" to the American bald eagle, hundreds of which have died from H5. Chris Purnell of BirdLife Australia notes the sea eagle regularly takes waterfowl — the same feeding behaviour that drove bald eagle deaths overseas. Local populations in Victoria and South Australia are already declining before the virus arrived. The most structurally vulnerable species is the Australian fairy tern, rated "very high" risk in the government assessment and already listed as vulnerable under national nature laws. The danger is concentration: in Victoria, the entire regional fairy tern population descended on a single breeding site last year. As Purnell puts it, one infected gull flying through could "potentially impact the whole breeding population within that site." This is the biosecurity equivalent of a single point of failure. Australia's waterbirds — pelicans and black swans especially — face compounding risks. Pelicans breed in rookeries of tens of thousands in inland Australia. Black swans carry a genetic vulnerability: 2023 genomic research led by Prof Kirsty Short at the University of Queensland found they lack immune gene components to detect H5N1 and mount a heightened inflammatory response when infected. Short describes them as a "sentinel species" — if H5N1 is in the area, black swans are likely to succumb. The brolga, one of Australia's two native crane species with deep Indigenous cultural significance, presents a different fragility. The Victorian population numbers just 600 to 700 birds. Internationally, thousands of cranes have died from H5. During winter flocking, when hundreds gather together, one or two infections could "spread like wildfire," Purnell warns. The structural pattern across all six species is the same: colonial breeding, long-distance movement, and first-time exposure to a virus that has been sharpening its lethality for five years on other continents. The policy response — vaccination of captive birds and wild little penguins — addresses the margins. The core problem is that Australia's most iconic bird populations concentrate at chokepoint sites where a single introduction event can cascade into population-level damage.
