Fledgling blue jays were among the disproportionately affected songbirds from the illness. Photo provided by Indiana DNR.

Seth Slabaugh
For HSPA

MUNCIE – Scientists investigating last year’s widespread songbird illnesses and deaths have eliminated some causes of the outbreak.

These include Avian influenza, West Nile Virus, mosquito-borne encephalitis, salmonella and chlamydia (bacterial pathogens), Newcastle disease virus, herpesviruses, poxviruses and trich parasites.

A list of suspected origins still holding the attention of state ornithologist Allisyn-Marie Gillet includes the birds having overindulged on cicadas, which possibly had bioaccumulated pesticides.

“The cicada hypothesis, personally I thought that seemed like a really plausible, credible cause,” Gillet told members of the Robert Cooper Audubon Society recently.

“The cicada theory was really compelling because the timing was perfect. The emergence of cicadas ended up coinciding really well with the emergence of this disease,” she said, referring to the billions of periodical cicadas that emerged from the ground over large swaths of the eastern United States last year.

The timing wasn’t the only connection. So was the distribution. The outbreak that caused eye discharge, crustiness and swelling, as well as tremors, disorientation and uncontrollable limbs in the birds, occurred in Eastern and Midwestern states, where the cicadas also were found.

One argument was that eating a poor diet, or a mono-diet, of mostly cicadas, due to their abundance, led to a vitamin A deficiency in the birds.

Gillet cited scurvy, a condition in people caused by not having enough vitamin C in their diets, as an example of how the lack of a vitamin can cause disease.

What sickened the birds, including many fledgling bue jays, grackles, starlings, Northern cardinals and American robins, remains under investigation by state and federal agencies, such as the Animal Disease Diagnostic Laboratory at Purdue University.
Tests completed thus far, Gillet reported, include necropsy (bird autopsy), histology (microscopic structure of tissues), virology (DNA), microbiology (growing cultures of bacteria from samples) and parasitology.

Ongoing tests include transmission electron microscopy (direct visualization of tissues), metagenomics (study of genetic material) and toxicology (vitamin A or pesticides), she went on, specifically alluding to DDE.

DDE is a breakdown product of DDT, a pesticide once widely used to control insects in agriculture and insects that carry diseases like malaria. DDT’s use in the U.S. was banned in 1972 because of damage to wildlife, but DDE persists in the environment, Gillet said, as a legacy contaminant.

The birds were eating a lot of cicadas, “which were underground for 17 years,” during which they “could definitely bioaccumulate” pesticides that “perhaps leached into the ground” and were absorbed by tree roots “that the cicadas were feeding off of,” Gillet said.

“However, there are some events that do not support this theory,” she went on. “We ended up with birds that were being tested in other states … like North Dakota … and Florida … and that’s not where cicadas were emerging, so that kind of made that theory more skeptical, not as strong a theory as one would have thought.”

But Gillet later told me: “I think pesticides – specifically, DDE, not other ones currently used – and cicadas are still being investigated … while also continuing the investigation of vitamin deficiency due to feeding only on cicadas.”
Cicadas and pesticides sound more likely to Gillet to have sickened the birds than some of the other theories she has heard, such as 5G (fifth-generation cellular technology).

It was in late May of 2021 that Gillet’s agency, the Indiana Department of Natural Resources, first began receiving reports of sick and dying birds in Indiana, starting with Monroe County.

In early summer, DNR announced a statewide moratorium on bird feeding to slow the spread of the illness, given the possibility that it was infectious.

The DNR says “wildlife disease events are often related to several interacting causes consisting of a pathogen, the environment, and the health of the host.” Though the investigation continues, unless the event repeats itself it is unlikely investigators will be able to identify a cause in the short-term.

However, Gillet says the agency did learn several important things:

There was a huge media response to the developing story. The DNR couldn’t deal with all of the one-on-one interview requests. Instead, the agency hosted a press conference on July 2 in which 20 media outlets participated. The bird event “made a huge impression across the country,” Gillet said. “People were really worried. I knew people loved birds, but I didn’t know they loved birds that much.”

“After the news releases, now came the public response to the huge media outpouring … The public was really concerned about birds dying, which is very heartening to hear. It makes me really happy to know that people do care about wildlife. And so a big lesson we also learned is that people do not want to be told to take down their bird feeders. This was a voluntary guidance moratorium. It wasn’t against the law to keep feeders up … But there were a lot of very angry people responding to us, and … we learned people really were listening.”

By the time the moratorium was lifted in September, the DNR had received about 4,300 reports from the public of sick or dead birds through its Sick or Dead Wildlife Reporting System.

“People were interested in songbirds and they were worried and they were on the lookout and provided help in tracking the disease. That was the biggest win of this event.” The agency could track the outbreak’s “severity and geographic extent pretty much in real-time thanks to the public.”

This article made available through Hoosier State Press Associaton.