Bird flu rampant among Black Vultures
New research shows how highly pathogenic H5N1 spreads through scavenging behaviour and causes large mortality events in North America
Mass mortality among a common scavenger
Highly pathogenic avian influenza has caused widespread deaths among Black Vultures across parts of the United States, according to a new scientific study examining the effects of the virus on this abundant scavenging species.
Researchers analysed carcasses and samples from more than 130 Black Vultures collected between 2022 and 2023 during the early stages of the H5N1 outbreak in North America. The virus was detected in a large majority of the birds examined, confirming that the species is highly susceptible to infection.
Large die-offs recorded
Many of the birds were discovered as part of mortality events in which multiple vultures died at the same location. Some incidents involved dozens of birds, while others reportedly involved more than a hundred individuals.
Field observations indicated that many affected vultures appeared lethargic or unable to fly or stand before dying. Neurological signs such as poor coordination or abnormal posture were also reported in some cases.
How the virus infects vultures
Unlike many waterbirds, which often acquire avian influenza through contaminated water, vultures appear to become infected primarily through scavenging.
The study suggests that the virus typically enters the body when vultures consume infected carcasses. Because Black Vultures often gather in large numbers at food sources, they may ingest high doses of virus while feeding alongside other birds.
Researchers believe this feeding behaviour may also allow the disease to circulate within vulture populations if birds scavenge on infected individuals.
Severe damage to multiple organs
Post-mortem examinations revealed extensive internal damage caused by the virus. The spleen and liver were frequently enlarged and severely damaged, with widespread tissue destruction observed in microscopic examinations.
Lesions were also commonly found in the digestive tract, kidneys, adrenal glands and other organs. In many cases the digestive system appeared to be the initial site of infection, supporting the idea that the virus entered through ingestion of contaminated tissues.
Why vultures may be especially exposed
Black Vultures are highly social birds that often gather at communal roosts and feeding sites. They are opportunistic scavengers, feeding on carrion ranging from wild animals to roadkill and waste at landfill sites.
This behaviour means that many birds may feed together on the same carcass, creating ideal conditions for disease transmission if the food source is infected.
Because they frequently return to the same feeding sites and roosts, outbreaks can affect large numbers of individuals within a short period.
Outbreaks beyond migration seasons
The researchers suggest the virus may initially reach vultures through infected migratory waterbirds, which are known reservoirs of avian influenza.
However, once introduced into a local vulture population, the disease may continue spreading through scavenging behaviour even outside the peak migration periods of waterfowl.
An ecological role worth protecting
Although Black Vultures remain widespread and numerous across much of the Americas, the findings highlight how vulnerable scavenger species can be to emerging diseases.
Vultures play a crucial ecological role by rapidly removing carcasses from the landscape, reducing the spread of pathogens and helping recycle nutrients in ecosystems. Monitoring disease outbreaks in these birds may therefore be important not only for wildlife conservation but also for broader environmental health.
The researchers say continued surveillance will be essential to understand how avian influenza may influence vulture populations and other scavenging birds in the years ahead.
March 2026
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