Virginia DWR gives insight into increase in black vulture bird flu deaths

RICHMOND, Va. (WRIC) -- A Virginia Department of Wildlife Resources (DWR) wildlife veterinarian has given further insight into the recent increase in reports of dead black vultures throughout the Commonwealth, which are due to bird flu.

Following the announcement by DWR on Monday, Oct. 20, that it had recently received reports of groups of dead black vultures across the state tied to avian influenza, or bird flu, 8News spoke with DWR wildlife veterinarian John Tracey on Thursday, Oct. 24, to learn more.

Black vultures are scavengers that serve an important role in the ecosystem. They help keep the ecosystem free of the bodies of dead animals, breaking down those organic materials and recycling them back into the ecosystem as nutrients.

Although vultures have a few conflicts with humans and animals, Tracey said they are overall beneficial to the environment.

"They are a critical component of our ecosystem, for sure," Tracey said. "That's not to say that they don't cause issues with humans or with domestic animals or with livestock occasionally; there's certainly conflict issues with black vulture, but overall, they serve a positive benefit to the ecosystem."

When asked why bird flu appears to be particularly affecting black vultures in Virginia, Tracey said there are a few possible theories.

Black vultures reportedly roost in dense nests, and they self-scavenge, meaning they eat the carcasses of their own species. Tracey said this can allow the virus to easily spread throughout the population.

"Because they roost in such dense populations in layers and layers on top of each other, and they will also self-scavenge dead carcasses if there's one sick or dead individual in the roost, they amplify the virus really well," Tracey said. "So, we can see these big mortality outbreaks in these roosts."

As for why this seems to have been ramping up within the last few weeks, specifically, Tracey posed that the migratory season of many birds, with a few dead birds possibly being undetected by the state with bird flu, may have introduced the virus to black vultures.

"It's possible that, as migratory season ramps up, we have low levels of infected birds coming through, and so there's maybe a small mortality, just a bird here and there that we don't really pick up, but then these vultures pick it up and then amplify it within the roosts," Tracey said. "So they might be serving, actually, as sentinel species for us right now, like, telling us we're starting to see an introduction of the virus."

Tracey further explained that it may be possible that in some roosts, the level of the spread of the virus and the immunity of the population may be fluctuating, but when it starts to get colder out during the fall season, a few sick birds may spread the disease throughout a larger group more easily.

"The other possibility is that in some of these roosts, there's maybe a balance between viral maintenance and population immunity that's waxing and waning," Tracey said. "And then, it starts to cool down, flu viruses like cold weather, and if population immunity starts to wane, we might have a couple of birds break, and again, they amplify the disease through the roost."

Regarding the possible effect of the influx of bird flu deaths of black vultures in Virginia on the environment, Tracey said that some research was done following an increase in bird flu deaths in black vultures back in 2022.

"Black vultures got hit very, very hard in 2022, so there was concern," Tracey said. "Like, 'what kind of population-level immunity is this having, are we going to have long-term ecological effects from this?'"

So long as overall population levels remain stable, Tracey said the outlook does not seem to be too severe.

"There was some work done modeling that, and they did demonstrate that we lost a significant part of the population, but that the population of the species overall was not at risk of long-term effects," Tracey added. "That's the original consensus, I guess. Time will tell if we continue to have repeated incursions into the species, if there are long-term effects for those species."

For Virginia residents, Tracey said anyone who sees a notable number of bird deaths should report them to DWR.

"Typically, when it comes to vultures or waterfowl, or other species of shorebirds, we recommend if you find five or more dead birds of a species over a period of a couple of days, then let us know," Tracey said. "If you find dead hawks, eagles or other raptors, then let us know."

"Even though this avian influenza virus does not routinely affect passerines and songbirds, if someone from the public does see high numbers of mortality, we usually say 10 birds or more, over a period of days, to let us know, and we can investigate it from there," Tracey added.

To report bird deaths to DWR, send an email to wildlifehealth@dwr.virginia.gov or call the DWR Wildlife Conflict Helpline at 855-571-9003.

For more information on bird flu, visit the department’s website.