Australia has recorded its first mass die-off of wild birds from highly pathogenic H5 avian influenza, after aerial surveillance spotted about 50 dead and 30 sick greater crested terns on Baudin Rocks, a small island off Cape Jaffa in South Australia. Samples from five terns and a silver gull tested positive at the national science agency CSIRO, federal Agriculture Minister Julie Collins confirmed on Monday. “This is the first confirmed case of a mass mortality and obviously a very concerning development,” she said.

The country had been the only continent free of the deadly strain until it was detected in mid-June. Since then, 74 cases have been logged across five states, mostly in migratory subantarctic seabirds such as giant petrels. The cluster at Baudin Rocks, however, signals that the virus is now exacting heavy losses among resident species. Collins said the event was not unexpected: “Sadly, we do know that once the H5 bird flu is spreading in wildlife and the natural environment, it is not possible to avoid significant losses, which is what we’re starting to see now.”

The detection of the virus in a silver gull has sharpened concern among authorities. Unlike pelagic terns, gulls range widely across coastal and inland habitats, mingling with other bird species and potentially acting as a bridge to waterbirds and poultry. Environment Minister Murray Watt warned that further mass mortality events are inevitable because wild birds cannot be contained. “This is the beginning of what is likely to be a long, difficult journey in terms of the impacts on wildlife,” he said. A national management plan has been activated, backed by an additional A$24 million from state and federal governments. No cases have been found on poultry farms, and officials assess the risk to human health as low.

Attention is now turning to Victoria, where aerial surveillance over the weekend identified a cluster of dead and sick greater crested terns in the Glenelg River estuary and on Lawrence Rocks. Samples have been collected, and if positive they would represent a second mass mortality event. In South Australia, a confirmed case in a petrel found in the Coorong wetlands has raised fears the virus may be moving from seabirds into important waterbird nesting areas. Authorities are urging the public to report sick or dead birds while avoiding contact, as the country braces for wider spread.