When a swamp harrier hawk—locally known as a kāhu—was discovered ensnared in a fence in a remote part of New Zealand’s North Island this past July, the initial reaction was one of indifference. Little did anyone realize that this find would soon etch the bird into the annals of history.
The very next day, after the hawk’s condition worsened, it was humanely euthanized. A routine examination that followed, however, revealed an unexpected twist: this was the first indigenous bird in New Zealand to test positive for H5N1 bird flu, a highly contagious and often deadly strain. This development came closely on the heels of the virus’s initial detection on the Australian mainland, which occurred only a month earlier.
“We’re more interconnected with Australia than we might think, despite the Tasman Sea separating us,” observed Jemma Geoghegan of the University of Otago, highlighting the fluid movement of birds between the two nations.
Now, a month later, the lethal virus is slowly infiltrating the region’s ecosystems. With two cases confirmed in New Zealand so far, authorities anticipate a significant spike in numbers as the virus continues its relentless march.
A month on, the virus is slowly making its way into the region’s eco-systems. New Zealand has recorded two cases of the virus but officials there expect that number to start climbing steeply any day now.
Australia, meanwhile, has just recorded its first mass casualty event: 49 dead greater crested terns and 35 sick ones were discovered on rocks off Cape Jaffa, an isolated outcrop on South Australia’s rugged limestone coast.
Both countries knew the virus was not far off when it was first detected on Australia’s remote sub-Antarctic Heard Island in 2025, leading to mass mortality of elephant seals.
By this time, preparations for the strain — which has ripped through every other continent — were well underway in New Zealand, where for the past two years the country’s Department of Conservation has been trialling a vaccination program for six species of “highly” endangered birds.
Two years ago the country began researching how certain native birds would tolerate and respond to the vaccine, so when the disease made its inevitable landfall, these populations could be protected.
“The trial was really to understand if the vaccine was going to be effective, but also what kind of doses different birds might need.”
She said this “targeted program” had been rolled out for species that were “really, really endangered” and already “highly managed” through GPS trackers and health monitoring.
The vaccine being used in New Zealand requires a booster shot to be effective, so it’s important that researchers are able to carefully track which birds have had the jab and which haven’t.
“Often they’ll be on offshore islands that are highly managed, because there’s only maybe a few 100 left of the individuals.”
New Zealand has so far vaccinated 196 of 300 targeted birds across six species.
While there is significant concern for both countries’ commercial poultry industries, there is acute concern for both countries’ native wildlife, which includes thousands of species not found anywhere else in the world.
Geoghegan said it was “hard to know” what the virus’ arrival would mean for these vulnerable populations, “because a lot of the native species here have not had exposure to even influenza viruses.”
Answering this question has been a huge part of Geoghegan’s research in New Zealand, and a key part of her country’s preparedness for the disease.
H5N1 does not affect all wildlife equally. Chickens, for instance, are particularly susceptible, while ducks are less so, so understanding which species are likely to be hit hard by the disease is important to understand.
Her research also focused on scavenger birds — like the kāhu — because they were likely to harbour more of the virus and therefore could become vectors for the virus once it arrived.
‘Scariest part of the whole story’
This kind of research is exactly the kind that Patrick Finnerty from the University of Sydney said had been missing in Australia.
“You probably find that answer most of the time is ‘we don’t really know’ [how bird flu will spread] and that’s kind of the scariest part of the whole story,” he said.
Finnerty said that Australia had not invested in a lot of the kinds of research that would have prepared ecologists like him to understand how the disease would move through different populations.
“We just don’t know how this disease is going to spread. So from a scientific perspective, we’re kind of at a bit of a loss because we don’t really know what this is going to do, and that’s terrifying.”
He said he was concerned this made it difficult for Australia’s response to understand how to protect birdlife.
Kirsty Short from the University of Queensland agreed: “I would have liked to see more investment in research on native species and H5N1 before the virus came here because I think we would have that opportunity to do a bit more scientifically informed preparedness planning.
“It just comes back down to the fact that we’ve just got such unique species here that we can’t really extrapolate from the northern hemisphere experience, so that does leave us a little bit vulnerable.”
She praised Australia’s surveillance of the disease, which she said was world-class, and believed that this would be an essential element of combating its spread.
When asked to compare Australia’s disease vectors to international experiences, she said no data came to mind because she said he hadn’t seen a country that had recorded the disease’s incursion as thoroughly as Australia.
“I can’t think of a country that’s documented it like we have, where it’s, ‘this is the first case. This is the second case,’ other countries just declare that they have H5N1 and that’s it,” she said.
Vaccine not necessarily the answer
Short said just like in New Zealand, the uniqueness of so much of Australia’s wildlife meant it was impossible to guess how the virus would affect different wildlife, and it was also impossible to know, without testing, how local wildlife would respond to a vaccine.
She said vaccine testing for certain endangered species was underway in Australia but did not have further details and believed the process for testing a vaccine on a wild population would take around seven months start to finish.
Short cautioned against seeing vaccines as a solution, though.
“You could say, ‘OK, well, let’s vaccinate all the endangered animals,’ but the practicality of going into the field and vaccinating endangered animals is limited,” she said.
“So probably what we’re looking at — and what other countries like Singapore have been exploring — is vaccinating captive animals that are at risk due to their endangered species or other reasons.”
