Scientists seek identity of mystery illness killing birds in Delaware and elsewhere | Delaware First Media
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Scientists seek identity of mystery illness killing birds in Delaware and elsewhere

Jul 16, 2021

Since May, wildlife officials and scientists along the East Coast and Midwest have been tracking a surprising number of sick or dying birds – but remain baffled by the cause.

Delaware has seen some cases reported locally and this week contributor Jon Hurdle takes a closer look at what we know and don’t know about this puzzling illness.


It has been about two months since Delaware’s wildlife officials received the first calls from people saying they had found a surprising number of sick or dying birds around their homes, but scientists still haven’t identified the cause of a mysterious condition that appears responsible for the outbreak in Delaware and other mid-Atlantic and midwestern states.

By mid-July, officials at the Department of Natural Resources and Environmental Control had ruled out some possible causes, including West Nile Virus and Avian Influenza, but were still searching for clues about what has killed some 75 birds in the First State and many more in states including Pennsylvania, Virginia, New Jersey, Ohio, Indiana, Kentucky, West Virginia, and Washington, D.C.

The mysterious condition results in eye-swelling and a crusty discharge, as well as neurological symptoms including erratic flight and stumbling, officials said.  The most-affected species appear to be familiar back-yard birds: common grackles, blue jays, European starlings and American robins, and young birds appear to be especially susceptible. There has also been some evidence of finches being affected.

This bird was found in the Washington DC areas suffering from the mysterious illness
Credit Leslie Frattarol / NPS

“This is a mortality event that is affecting birds on sort of a large scale, not just our state,” said Jordan Terrell, an environmental scientist with DNREC. “It’s definitely concerning in terms of large numbers and how long this event may last. We are assuming that there are birds out there that are not getting reported that are also being affected by this.”

Terrell said scientists in Delaware and other states are considering all options in their search for the origins of the outbreak, but had yet to explain it.  “We have many things pending but unfortunately no answers at this point,” she said.

Still, she said in early July that there were signs that the condition’s spread was slowing. “It’s more stable than getting worse. We’re hopeful that in the next few weeks, that cases will be dwindling but no guarantees there.”

Terrell said dead birds should be reported to DNREC, while live birds with symptoms of the mystery illness should be taken to Tri-State Bird Rescue, a Newark-based nonprofit that will try to save them but which so far has been unable to do so, she said.

“We have not had much success in rehabilitating these birds back to health but we are encouraging people with live birds with those symptoms to call Tri-State Bird Rescue for birds in Delaware,” she said.

Lisa Smith, executive director of Tri-State, said her group, too, was seeing a slowdown in the number of birds received with symptoms of the illness.

She said the group has so far taken in 22 birds from Delaware, four from Maryland and four from Pennsylvania, but in the absence of a diagnosis, the chances of survival for any of the patients were slim.

“Sadly, there is no treatment at this time for this disease,” she said.

"Currently, we know more about what is not causing these symptoms and deaths than what is causing them." - Margaret Brittingham, Penn State University College of Agricultural Sciences

According to media reports, there may be a link between the illness and this year’s “brood X” cicada outbreak – a theory that’s based on a correlation of timing and geography. But Margaret Brittingham, professor of wildlife resources at Penn State University’s College of Agricultural Sciences, said that hypothesis is just speculative. She said that only a laboratory diagnosis will isolate the cause.

For now, the investigation has made more progress in ruling out possible causes than in identifying a culprit, she said in a statement on July 7. “Currently, we know more about what is not causing these symptoms and deaths than what is causing them,” she said.

Matt Sarver, conservation chair of the Delaware Ornithological Society, said he wasn’t surprised that scientists haven’t yet identified the cause of the outbreak, given what he said was a shortage of funding for wildlife research at state and academic institutions.

He said the outbreak appeared to be less of a threat than other pathogens such as West Nile Virus because the new illness appears to affect mostly juvenile birds whereas the other conditions also affected adults, with a greater effect on the populations of those species.

Dead birds collected by DNREC are sent to veterinarians at the University of Pennsylvania’s New Bolton Center which is using diagnostic techniques in an attempt to find a cause. The center declined to comment, referring calls to state wildlife officials.

Although the cause of the illness is still being investigated, wildlife-health experts suspect that congregations of birds at backyard feeders and bird baths are contributing to its spread, and so they have urged homeowners not to use the features that attract birds to their yards.

Residents are also advised not to handle wild birds, or to use disposable gloves if they do; to keep pets away from sick and dead birds, and to clean bird baths and feeders with a 10 percent bleach solution whenever officials say it’s safe to put them out again.

As people take down their feeders, they are buying a lot less feed from Wild Birds Unlimited, a Hockessin-based seller of bird food, said Charles Shattuck, co-owner of the business.

He said there’s been a “dramatic” decline in his sales as customers call him for advice, and then follow the state’s recommendations. Shattuck said he refers callers to DNREC’s advice, and tells them to make their own decisions about whether to keep feeding birds.

"They love their birds, they don't want to see anything happen to them. They will do whatever it takes to protect them." - Wild Birds Unlimited co-owner Charles Shattuck.

“We’ve been fielding phone calls almost 24 hours a day since July 1, people asking what to do, where it is, and what’s going on,” he said. In response, he said he has been sending out weekly emails trying to help his customers recognize that birds die every day from a variety of causes such as cats, pesticides and window strikes, and that the new illness is another source of mortality, albeit one that has not yet been explained.

“They love their birds, they don’t want to see anything happen to them, they will do whatever it takes to protect them,” Shattuck said, adding that DNREC’s estimate that 75 Delaware birds have died from the illness so far was likely just a “percentage” of the total.

While the official number of bird mortalities in Delaware may not be very high so far, Terrell said DNREC issued a press on June 30 to alert the public, and to try to understand more about the problem.

“This is something that we wanted the public to be aware of, to hopefully diminish the effects of this mortality event by limiting the amount of congregating birds in our back yards,” she said. “Also, for the public to report these sick and dying birds so that we can get an idea of what is happening in the field because we can’t physically be everywhere.”

By July 13, the diagnostic work had still not yielded an explanation for the bird deaths, according to Michael Globetti, a spokesman for DNREC.

Federal officials, too, are looking into the outbreak. On July 2, the U.S. Geological Survey issued an updated statement saying that a battery of tests are being run by federal, state and academic institutions but that “no definitive causes of illness or death have been determined at this time.”

Still, the agency said it has received no reports of the condition spreading to humans, domestic livestock or poultry.

In New Jersey, the state’s Audubon Society is on alert for cases, and will work with state officials to contain any outbreak, said Eric Stiles, president of the conservation nonprofit.

“We haven’t heard of any confirmed deaths in New Jersey but we are supporting the NJ Division of Fish and Wildlife in asking for people to report any information to our state agency to inform any required science-based rapid response,” Stiles said on June 30.