H5N1 Bird Flu Arrives in Australia, Threatening Birds and Their Habitats

The highly pathogenic H5N1 strain of avian influenza was first detected on the Australian mainland in June. Since its arrival, the virus has caused mortality among petrels and crested terns, and scientists warn that other species could soon follow.

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Australia’s roughly 850 bird species perform a wide array of ecosystem services. Ground-dwelling birds such as orange-footed scrubfowls and Australian brush-turkeys turn over soil, enhancing aeration and seed germination. Waterbirds—including black swans, whistling ducks, and musk ducks—disperse seeds and regulate aquatic invertebrate populations. Nectar-feeding honeyeaters and lorikeets act as primary pollinators for many eucalypts and other native flora, while raptors such as falcons help control pest species by culling weak or diseased prey.

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Authorities estimate that about 30 % of Australian bird species face high to extreme risk from H5N1, with five species classified at extreme risk of possible extinction. Overseas experience shows that the virus can decimate colonies of black-headed gulls and halve populations of coastal peregrine falcons. If insect-eating birds decline sharply, eucalypts already stressed by drought may suffer increased mortality because fewer birds will consume sap-sucking psyllids and leaf-eating weevils. In tropical rainforests, reduced numbers of cassowaries, pigeons and doves could limit seed dispersal, shrinking tree distributions and genetic diversity. Similarly, in arid central regions, declines in emus, pigeons, parrots and finches may lead to the loss of certain grasses and shrubs. A drop in honeyeater and lorikeet populations would also curtail cross-pollination, forcing plants to rely on wind or less mobile pollinators, which can increase inbreeding and lower fruit and seed output.

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While the full extent of species loss remains uncertain, experts stress that protecting birds from additional threats—such as habitat loss, invasive species, and climate stress—can bolster their resilience. Observations of thriving galah flocks feeding on invasive onion grass illustrate the adaptive capacity of some species. Continued monitoring, biosecurity measures, and habitat conservation are viewed as essential steps to safeguard Australia’s avian diversity and the ecosystems that depend on it.

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