Experts Continue to Investigate Deadly Bird Disease

They've ruled out several causes including West Nile virus and avian flu.

Close-Up Of Blue Jay Perching On Bird Feeder
Young blue jays are some of the birds affected. Brandi Niles / EyeEm / Getty Images

A mysterious illness continues to affect songbirds as it keeps spreading through the Mid-Atlantic and Southeastern United States. Experts have ruled out some causes, but are recommending that people take down feeders until the exact cause of the epidemic is known.

Wildlife managers began getting reports in April in Washington, D.C., of sick and dying birds with crusty, swollen eyes. Soon, there were similar cases spotted in Maryland, Virginia, West Virginia, and Kentucky.

Then reports were coming in from even more states across the Northeast and in some Southern states.

Most of the birds affected were common grackles, blue jays, European starlings, and American robins. But some other species of songbirds have been spotted too.

The United States Geological Survey's National Wildlife Health Center (NWHC) has been working with state and federal agencies to diagnose the cause of the disease.

So far, they've ruled out West Nile virus and avian flu which, the Audubon Society points out is good news because both of these viruses occasionally can infect people.

They've also eliminated salmonella, chlamydia, Newcastle disease, herpesviruses, poxviruses, and trichomonas parasites.

Although these causes have been rejected, no cause has been determined yet. Thousands of sick and dying birds have been reported to federal and state agencies so far and research is ongoing.

"Transmission electron microscopy and additional diagnostic tests, including microbiology, virology, parasitology and toxicology, are ongoing," according to the NWHC.

In the meantime, there is much speculation.

One popular theory suggests a link between the illness and the advent of the Brood X cicadas this year. Upon emerging after 17 years, some of the insects carry a deadly fungus. Researchers have questioned whether the birds have been infected with the fungal spores when they eat cicadas.

Others wonder if cicadas have been sprayed with insecticide which the birds ingest when they get the insects. 

In addition to crusty, bulging eyes, many of the birds also have neurological issues such as balance issues, head tremors, or disorientation before they die.

What Bird Lovers Should Do

Until the cause of the mysterious disease is found, ecologists advise home owners to stop feeding the birds in the areas where the sick birds have been spotted. Birds congregating in groups is how disease can easily be transmitted.

Don't worry about birds not having enough to eat if you empty your feeder and bird bath.

"Bird feeding is really only a supplement to their natural diet, not a make or break situation of survival. There is plenty of natural food around for the birds," Marion E. Larson, chief of information and education for the Massachusetts Division of Fisheries & Wildlife, tells Treehugger.

"Birds have been around for thousands of years—long before anyone thought about feeding them! Same for water sources—birds get their hydration from dew on grasses and plants, caterpillars, insects as well as from ponds, lakes , streams and wetlands."

Experts have also suggested that people clean bird feeders and bird baths with a solution of 10% bleach and water. They're also asking pet owners to keep pets away from sick or dead birds.

Although there’s no evidence that the disease is transmissible to humans, officials are advising people to avoid handling the birds. If you must remove dead birds, wear disposable gloves and place them in a sealable plastic bag in the household trash.