Australia is racing to vaccinate 5,000 of the world’s smallest penguins against bird flu. The drive is believed to be the largest wild-bird vaccination program ever attempted.

The program targets little penguins at Phillip Island and St Kilda in Victoria. More than 1,000 birds have already received their first dose of the H5N1 vaccine. Each penguin needs two doses, with the second given three weeks after the first.

Teams work at night as the penguins return from the sea. The birds are guided into small pens, then weighed, measured and microchipped before vaccination. The microchip helps workers identify each bird for its second dose.

Phillip Island is home to about 40,000 little penguins, the world’s largest colony. Its famous Penguin Parade draws about 700,000 visitors a year and contributes around 500 million Australian dollars to Victoria’s economy.

Worst-case modelling suggests a major outbreak could kill between 8,000 and 16,000 birds. H5 cases have already been confirmed in little penguins on Phillip Island and Kangaroo Island.

Catherine Basterfield of Phillip Island Nature Parks said catching the penguins is challenging but is being done by trained specialists.