Last Saturday, as night fell, a gaggle of volunteers and scientists gathered along the rocky coastline of Victoria’s Phillip Island (Millowl).
They weren’t congregating for the dramatic scenery before them, but for what streamed in from above: an enormous flock of short-tailed shearwaters (Ardenna tenuirostris) which were heading back to their burrows for the night.
“At dusk, it’s just amazing — tens of thousands of birds coming in from the ocean, flying over you and around you,” virologist and keen birder Michelle Wille said.
With head torches at the ready, Dr Wille and her crew were one of many surveillance groups around Australia who test flocks for avian influenza, with an eye out for a particularly deadly type.
The H5N1 2.3.4.4b strain of the virus has already killed hundreds of millions of wild and domestic birds and mammals around the world.
But not here — yet. Australia is the last continent free of the disease.
The National Avian Influenza Wild Bird Surveillance Program, managed by Wildlife Health Australia, samples wild birds for influenza year-round, and springtime is particularly important.
As migratory species fly from bird-flu-affected regions to our shores to feed and breed during our warmer months, they may bring the virus with them.
Last year, for instance, H5N1 2.3.4.4b was detected in short-tailed shearwaters in Alaska, where the birds spend the Northern Hemisphere summer before making the epic 16,000-kilometre weeks-long journey across the Pacific Ocean to Phillip Island.
“So we thought it would be prudent to include short-tailed shearwaters in our program … because we have very little data on the species,” Dr Wille said.
So with millions of birds arriving, not to mention the wild birds living in Australia year-round, how do scientists, birders, Indigenous rangers, biosecurity officers and other groups keep tabs on their health?
The answer involves techniques familiar to many of us from the early days of the COVID-19 pandemic.
How to test a wild bird
“Environmental samples” — faeces collected from bird habitats — can give scientists an idea of viruses present in flocks, but samples taken directly from an animal give more accurate results.
And to test a live wild bird for avian influenza, they first must catch it.
Dr Wille and her colleagues work with dedicated “catching teams”, usually comprising members of volunteer organisations, who get hold of and ensure the welfare of the birds.
Exactly how they catch a bird is tailored to the bird type.
For seabirds, such as short-tailed shearwaters, it’s generally a matter of waiting for them to touch down at their nesting colony. After landing, they toddle towards their burrow.
“The thing with seabirds is they’re designed for the sea, but they’re not very good on land,” Dr Wille said.
Short-tailed shearwaters can’t take flight quickly, so members of the catching team simply scan the ground with their head torch beams and pick the birds up.
Then there are shorebirds, also known as waders. They forage for food in mudflats and along shorelines, so are much faster and more nimble than their mostly seafaring counterparts — far too quick to be scooped up by hand.
So, Dr Wille said, catching teams use methods such as “cannon netting”.
It’s exactly how it sounds: a big net, 13 by 10 metres, scrunched into a ball and fired out of a small cannon.
The third group are waterfowl — ducks, geese and swans.
They can be caught under cannon netting too, but there is an easier way, according to Dr Wille.
“Ducks like food, so you put baited traps in places like dams, and the duck will just come in by itself.”
How to test a bird for flu
Back on Phillip Island last weekend, with short-tailed shearwaters safely picked up by the catching team, the “processing” team — including Dr Wille — stepped in.
These highly trained individuals were responsible for collecting samples, gently swabbing inside each bird’s mouth and cloaca, and popping the swab into a tube.
They also took tiny blood samples from wing veins, similar to how someone with diabetes pricks their finger to check blood sugar levels.
The birds then rejoined the flock.
Short-tailed shearwaters are at sea for months at a time, and rest on the surface of the ocean when they need a break. (Flickr: Short-tailed Shearwater, Tom Benson, CC BY-NC-ND 2.0)
During the two-night trip, Dr Wille and her processing crew took around 240 samples.
Those samples were brought to the World Health Organization Collaborating Centre in Melbourne’s Doherty Institute, where Dr Wille ran tests.
She analysed blood samples for antibodies, which can give scientists an idea if a bird was infected with any type of avian influenza at some point in the past few months.
The swabs, meanwhile, let Dr Wille look for fragments of avian influenza virus — using the same PCR test process used with COVID-19 — which would signify a current infection.
What if I find a sick or dead bird?
When the disease is detected in Australia, national, state- and territory-based plans will kick into action.
“Health monitoring, biosecurity measures and increased communications would all be important aspects of a government response to H5N1 in wildlife, domestic poultry and other types of birds,” Victoria’s chief veterinary officer Graeme Cooke said.
“This could include the possibility of movement restrictions on susceptible animals. Similar measures were undertaken in the recent H7 avian flu outbreak in Victoria.”
The red-necked stint (Calidris ruficollis) can fly thousands of kilometres without a break as they travel between hemispheres. (Getty Images: Earnest Tse)
In the meantime, people such as Dr Wille form the biosecurity frontline of bird flu surveillance, but they can’t monitor all birds everywhere all the time.
If you find sick or dead wild birds, do not touch them. Report them to the Emergency Animal Disease Hotline on 1800 675 888.
This weekend, Dr Wille is off to a site near Koo Wee Rup, south-east of Melbourne and not far from Phillip Island, to catch and take samples from shorebirds called red-necked stints (Calidris ruficollis).
These tiny birds are among the smallest of the shorebirds. They weigh about as much as two AA batteries, but make the return trip between Victoria and Siberia every year.
Whether they’re also carrying a lethal viral passenger remains to be seen.
