A shimmering azure sky pierced by darting white shapes, far out to sea and coming closer. Greater crested terns on the wing, hunting fish in the calm, silky waters of the Derwent off Long Beach, Lower Sandy Bay.
It was a delight to see them bowing their heads to spot fish just below the surface of the water, then tilting their long, pointed wings before dropping likes stones, hitting the waves with a splash and then emerging with a wriggling, silver fish, in their yellow beaks.
A day marked by a little heartbreak, however. Earlier on breakfast television I had seen an account of a large number of crested terns dying at a colony in south Australia. Clearly, the culprit was avian influenza.
Bird flu has been slow to reach Australia after hitting bird populations throughout the world, including Antarctica. But there were warning signs in late June when a migratory seabird from the south, a brown skua, was found in great distress on a beach in Western Australia. It was soon confirmed the bird was suffering from the disease.
Reports of other victims soon followed, alarmingly some of them Australian resident species which had clearly been affected in Australian waters. Among these have been silver gulls and the terns.
Already the disease has struck both birds and elephant seals on an Australian territory, Heard Island in the southern Indian Ocean, and biosecurity officials are braced for a worst-case scenario – the virus carried into poultry farms.
Avian influenza, or H5 bird flu, refers to various strains of influenza A viruses that primarily infect birds. The H5N1 strain has been particularly concerning due to its ability to infect not only birds but also mammals, including humans. The virus is typically spread through contact with infected birds or their droppings, and it can lead to severe illness in both animals and humans, although the latter is rare. The avian flu virus that dominates headlines today is traced back to a single strain isolated from a goose in southern China in 1996.
The mass mortality of the crested terns is particularly worrying because certain species are particularly vulnerable. In Britain, a colony of 150,000 gannets has been reduced by a third and may take decades to return to previous levels.
In Australia, the black swan is found to have low resistance along with the terns. Bird flu also poses a risk to endangered species with small populations, the orange-bellied and swift parrots included.
With one in six birds in Australia under threat from factors other than bird flu, Birdlife Australia is calling for a greater government effort to address the major factors of bird decline -– land-clearance and habitat loss along with climate change. The organisation is campaigning to persuade the government to invest $200 million in “a nature resilience package” to strengthen wildlife populations and improve preparedness for bird flu.