Bird flu has killed thousands of southern elephant seal pups on remote Antarctic islands belonging to Australia, new research has shown.

Heard and McDonald Islands, about 4,000 km (2,485 miles) south-west of Australia, are home to over one million breeding seabirds and seals.

Scientists, using data from last October and this January, estimate about 13,000 baby seals from a group of 17,000 on Heard Island were killed by the H5N1 strain of bird flu since last August, more than 75% of the entire group. They also found higher than expected deaths in penguin populations.

Australia is the only continent with no cases of the H5N1 strain which has spread among birds worldwide and affected some mammals.

This latest research, published in the scientific journal BioRxiv and yet to be peer reviewed, was based on drone surveys and ground visits to the hard-to-reach islands where scientists collected samples from nine species.

Of those, six species tested positive for the H5N1 strain: the southern elephant seal, king and gentoo penguins, the Antarctic fur seal and the South George diving petrel.

Late last year, scientists were alerted to the possible impact of bird flu on the islands when a research voyage found hundreds of dead baby seals.

More research conducted this January confirmed bird flu had mainly hit southern elephant seal pup populations with a smaller impact on king and gentoo penguins.

The report estimates that 13,359 baby seals from a population of 17,364 on Heard Island died, more that 75% of the entire group. The mortality rate may be an underestimate as pups were still dying at the time of the final surveys, researchers said. In one area 97% of baby seals had died.

Elsewhere, data showed several hundred adult king penguins died, which was a low proportion of the population but above normal levels.

"These observations of H5 bird flu at Heard Island and McDonald Island are the first detection in an Australian external territory and show the continued eastward movement of the virus around the sub-Antarctic," lead author wildlife biologist Dr Julie McInnes said.

"Our results show a similar pattern to other sub-Antarctic islands, such as South Georgia, where elephant seals have been hardest hit."

The report also found no unusual deaths among the albatross population or two endemic species, the Heard Island shad and the black-faced sheathbill.

Environment Minister Murray Watt said the seal deaths were "sobering" and showed Australia must not be complacent in preparing for the strain possibly making it to the mainland.

"We must be realistic about the likelihood of an incursion here, and plan accordingly."

Scientists believe bird flu was likely introduced to the islands last August from migrating birds from the French-owned Crozet Islands, about 1,800 km away.

The Australian Antarctic Program, a partnership between government and research institutions, will continue to monitor for signs of bird flu in its territories.