An emergency response plan has been launched in Victoria after its first positive case was confirmed on Thursday in a bird near Portland in the state's southwest.
Another was confirmed in a giant petrel, a sub-Antarctic species found at Port Lincoln in South Australia, bringing the total number of confirmed Australian bird flu cases to 28.
Confirmed cases of the deadly strain have also appeared at Western Australia, NSW and Queensland.
Thirteen new suspected cases have also been found in a native seabird colony in SA after local transmission was confirmed by state authorities.
The disease, which has devastated bird populations worldwide and has also killed tens of thousands of mammals, arrived on Australian shores in mid-June.
Victoria's chief biodiversity officer James Todd said authorities around the nation had been preparing for a potential detection given the annual movement of migratory birds to Australia.
He said bird flu presented a risk to more than 600 native species in Victoria.
They include a number of critically endangered species kept in captivity by Zoos Victoria for conservation and captive breeding programs.
Victoria's official bird emblem, the helmeted honeyeater, is also at risk along with the orange-bellied parrot, plains-wanderer and regent honeyeater.
Alarm bells are ringing for conservationists after one case was confirmed near a key colony of Australian sea lions on SA's Kangaroo Island, an endangered species with a population of just 12,000.
They warned the virus was moving exactly as predicted and pushed for further investment to protect Australian wildlife.
"We need to stop thinking about bird flu as a series of isolated detections and start responding to it as a national wildlife emergency," Invasive Species Council advocate John Kelly said.
He called for a federal $200 million investment to strengthen wildlife resilience.
Bird flu has caused havoc in the poultry industry globally, causing the deaths of about 140 million birds since January last year.
Victorian Farmers Federation president Ryan Milgate said the virus' detection was not unexpected and claimed the state industry was prepared "for this very moment".
He encouraged farmers to review their biosecurity plans and remain alert for any sick or dead birds as well as unusual signs of disease around their property.
Victoria's chief veterinary officer Dr Graeme Cooke said contingency plans had been scaled up to prepare the sector for the virus' arrival.
"We are extremely well prepared, relative to the situation that other countries may have been found unprepared for," he said.
Australia's Chief Veterinary Officer Beth Cookson said the risk to human health remained low.
There was no evidence of any mass mortality events and no detections in poultry or in our agricultural production system, she said.
Samples from the 13 suspected SA cases - all greater crested terns - found in Port Lincoln have been sent to the CSIRO's Australian Centre for Disease Preparedness in Geelong for testing.
People are being urged not to touch sick or dead wildlife, but to record the location and report it to the Emergency Animal Disease Hotline 1800 675 888.
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