As scientists rule out some causes of bird illness, questions — and theories — abound

Since late May, wildlife managers in at least nine states have received reports about sick and dying birds — primarily fledgling common grackles, blue jays, European starlings and American robins — with swollen, crusted eyes and neurological symptoms, according to a release from U.S. Geoological Survey that was updated July 2.

What began in Maryland, Northern Virginia, West Virginia, Kentucky and Washington, D.C., has since been reported in Delaware, New Jersey, Pennsylvania, Ohio, Indiana and perhaps Southwest Virginia, according to officials with Southwest Virginia Wildlife Center of Roanoke.

At least three samples of birds were recently collected by the center, said Assistant Director Chester Leonard. The samples will be analyzed by the Virginia Department of Wildlife Resources for confirmation.

“Unfortunately they’re just not giving us a lot of information right now,” Leonard said of the state. “We can’t confirm for sure until we get results back.”

People who see a dead bird — and not just a songbird — can take a picture and report it on the Department of Wildlife Resources website.

“We’re just trying to figure out what’s going on here,” Leonard said, reminding people to remove their birdbaths and feeders for a while, and sanitize them. “If it is spreading here, we just want to be reducing the numbers as much as possible.”

What it isn’t

At this point, it’s still unclear whether the avian ailment has spread to Roanoke, or whether it even does spread. State wildlife veterinarian Megan Kirchgessner said in an email Tuesday that the Department of Wildlife Resources had not yet received verifiable reports of suspiciously ailing birds in southern parts of Virginia, and that the preliminary reports from the wildlife center seemed unlikely.

“At this time, I do not consider it a sure bet that this event will spread to other parts of the Commonwealth,” Kirchgessner said. “In Virginia, based on reports we are receiving, it appears to have remained fairly localized in NOVA and the northern Shenandoah Valley and has not yet spread south.”

The ailment has no definitive cause at this time, according to the U.S. Geological Survey release. But through laboratory diagnostics, a handful of state facilities and university departments have tested to determine what pathogens are verifiably not present in the dead birds.

According to that research, the illness isn’t caused by a bacterial agent like salmonella or chlamydia, and it’s not bird flu, West Nile or others in those viral germ families. Nor is it some form of herpes, pox virus or sexually transmitted parasite.

With more lab tests ongoing, guesswork continues among birdwatchers and experts.

Dana Hawley, a Virginia Tech professor of biological sciences whose research includes bird pathology, said she has heard a number of theories. All are uncertain and most are unlikely.

“I’m not terribly optimistic that they’re going to necessarily know very soon what’s going on, just because there are so many possibilities,” Hawley said. “And it can also be multiple causes that sort of interact with each other.”

Some have suggested that the bird deaths are caused by pesticides, because of the presence of seizures and other neurological effects.

“I don’t really buy the pesticide theory myself,” Hawley said. “It seems very unlikely to me that people are spraying sufficiently high loads of pesticides that would suddenly be affecting bird populations.”

Emergent 17-year cicadas screaming from the trees this summer in afflicted areas also seem unlikely to cause the die-offs, Hawley said.

“People have been spraying pesticides for centuries, and cicadas have been emerging every 17 years for centuries,” Hawley said. “My thinking is that it’s got to be something more unusual.”

Perhaps it is a particular fungal toxin being consumed now by insects, causing the toxin’s effects to amplify in birds further up the food chain. But that’s just a guess, she said, based on one of several theories circulating.

“The other thing is it’s maybe been some kind of new infectious disease, and that’s certainly possible,” Hawley said. “I am hopeful that it’s not something contagious.”

Something like a fungal toxin would be preferred because it would not be transmissible from bird to bird like an infectious disease, negating the need to hide away bird feeders, Hawley said.

A continuing mystery

Whatever the underlying cause of the avian affliction, there’s no telling how long it might take to uncover.

“It’s a mystery,” Hawley said. “I hope it doesn’t take over two decades to figure out, like the bald eagle one.”

For more than 25 years, up until this March, scientists contended with a mysterious case of bald eagles dying across the southeastern United States. With decades of effort, researchers discovered a combination of manmade and natural factors that introduced a new type of bacteria to the ecosystem, killing the eagles consuming it in magnified volumes through their apex predator diets.

“With this many people across the country trying … I suspect they will figure it out quickly,” Hawley said. “It’s an interesting example of how sometimes these things are really complicated and can take a long time to nail down.”