If seabirds contract avian flu by stealing food from infected birds, it offers valuable information for scientists on where to look for outbreaks among these at-risk bird species.
The H5N1 avian influenza virus, a lethal strain that has resulted in the deaths of millions of birds worldwide since 2021—and, in rare instances, can be passed to humans—might be transmitted through the food theft habits of certain seabirds.
A study released today in the journal Conservation Letters emphasizes kleptoparasitism, a behavior where species like frigatebirds and skuas provoke other birds to regurgitate their food, as a potential method for the transmission of avian flu.
Researchers, led by scientists at UNSW Sydney’s Centre for Ecosystem Science and including collaborators from BirdLife International, Deakin University, and Monash University, examined data on the distribution, behavior, and movement of frigatebirds and skuas. They also sifted through a global database to identify cases of these birds contracting the virus and explored which seabird species frigatebirds and skuas commonly target for their kleptoparasitic behavior.
According to lead author Simon Gorta from UNSW Science, the research could provide a new lens for investigating how and where the virus spreads and how it can be transmitted between individual birds, different populations, and across large regions.
“Understanding how the virus is transmitted is vital for monitoring and management efforts, especially when it concerns vulnerable species or areas, and it also sheds light on potential threats to other animals and humans,” explains Gorta, a PhD candidate at UNSW.
“Though the first H5N1 virus was identified in 1996, the current 2.3.4.4b strain has proliferated much more than earlier strains, proving to be highly deadly, claiming hundreds of thousands of wild seabirds since its first detection in 2021.”
Initially limited to Eurasia and Africa, the virus spread to North America in 2021 and subsequently to South America in late 2022. By early 2024, it reached Antarctica and has been classified as a panzootic, meaning a pandemic affecting animal species.
Seabirds at risk of transmitting the virus
Marine birds, including seabirds, have been particularly impacted by this panzootic.
“Seabirds are among the most endangered birds on earth, and it is alarming that they are particularly susceptible to such diseases,” remarks co-author A/Prof. Rohan Clarke from Monash University.
Co-author Professor Richard Kingsford notes that seabirds are especially at risk due to their breeding habits.
“The close quarters in which seabirds breed raise concerns over transmission, as close contact and potential contamination of shared resources occur on crowded breeding islands, in addition to behaviors such as predation and scavenging from infected individuals,” he explains.
However, the researchers suggest that kleptoparasitism—an established behavior among seabirds, especially frigatebirds and skuas—could also play a significant role in the virus’s spread.
Kleptoparasitism involves one bird stealing food from another by compelling it to regurgitate its meal. If the victim bird is infected, the regurgitated food might carry saliva laden with the virus, thereby infecting the kleptoparasitic bird and potentially allowing it to transmit the virus to others.
The research indicates that this transmission route could introduce the disease to new populations and could even span long distances if infected birds migrate.
“Many seabirds, including the kleptoparasitic species studied, migrate across vast distances, covering tens of thousands of kilometers,” notes Alex Berryman, Red List Officer for BirdLife International.
“If these kleptoparasites become infected during their migrations and subsequently encounter other birds in a manner that supports transmission, the disease could infiltrate new, vulnerable populations that have not been previously exposed,” warns Berryman.
Importance of early detection
As the H5N1 2.3.4.4b strain has not yet reached Australia, proactive monitoring for early detection of the virus when it arrives—rather than if—is already in progress.
“Globally, birds face unprecedented threats, making it essential to properly investigate and manage the risks associated with bird flu,” asserts Gorta.
“We have identified that migratory kleptoparasitic species, alongside predatory and scavenging birds, may be among the first to become infected once H5N1 arrives in Australia.”
This information will assist in the coordinated management of avian influenza in Australia, particularly under the National Avian Influenza Wild Bird Surveillance Program.
The team emphasizes the significance of these findings in preparing Australia for the potential arrival of the virus, especially regarding its vulnerable subantarctic islands.
