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Mysterious bird deaths in the eastern US - What is killing Blue Jays?

Updated: Nov 13, 2021

Mass die-offs of common yard birds in the eastern United States have raised the alarm about feeding birds, pesticides, and heatwaves this summer.

In many Atlantic, Appalachian, and Great Lake states, birds are suffering and dying from an unknown disease or affliction. Rehabbers, researchers, and agencies are racing to determine the underlying cause that may have already caused several thousand bird deaths. However, even after weeks of searching, there are no answers, and conservationists are left unable to offer much help.

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Update #1 (08/14/2021): There are reports that the deaths are beginning to subside. It may be safe to return your feeders to normal use, however, please be diligent in cleaning your feeders!

What is the cause of the bird fatalities in the eastern US?

Currently, there is no known, or accepted, cause behind these fatalities. However, various ornithologists, conservationists, state agencies, and federal agencies have offered potential diseases and other maladies. One of the leading theorized suspects is the Brood X cicada hatch. Many bird biologists believe the cicadas are being treated with pesticides, and the birds are consuming the cicadas as they die. When the birds consume many of these 'easy meals,' they build up large amounts of the pesticides in their body, or in the bodies of the nestlings being fed the cicadas, leading to the symptoms described above. Not all researchers agree, however, due to some deceased and symptomatic birds coming from areas where the hatch was lessened. However, there may be multiple issues across this large range.


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Other potential problems may be tied to a well-known bacterium, Mycoplasma gallisepticum. Mycoplasma bacteria are responsible for the well-known "House Finch eye-disease" frequently found in feeder birds. And while officials are reporting this bacterium is being found in many of the deceased birds, the symptoms and species do not match the typical outbreak of mycoplasmal conjunctivitis at feeders.

West Nile virus, salmonellosis, avian flu, and other diseases have also been considered, but most who are studying these afflicted birds have ruled these diseases out, so far.

Which birds are being impacted?

Currently, the species most impacted are larger birds like Blue Jays, Common Grackles, European Starlings, and American Robins. These symptoms have not been reported in other species, however, it may be other species are less easily found during the symptomatic phase of this issue.

A fledgling Common Grackle displays poisoning or disease symptoms while sitting on the ground.
A fledgling Common Grackle exhibits the symptoms seen in hundreds of other birds across the eastern US.

The individuals most impacted within the afflicted species are nestlings. Why? If we move away from just writing only the known, and put on a sleuthing hat, our flocking opinion falls back to pesticide bioaccumulation. We think adult birds are finding cicadas that are dead or dying, grabbing them, and then feeding them to nestlings and fledglings. After being fed tens of these cicadas, these despicable poisons are building up in the tissues and organs of these young birds and doing damage far beyond their purpose of killing cicadas that are a crucial part of the natural cycle. A wildlife rehabber, Katie Fallon of the Avian Conservation Center of Appalachia, noted that a similar outbreak occurred in 2016 in their region, which coincided with the Brood V hatch. However, this connection is pure flocking speculation on our part.

What are the symptoms of this outbreak?

The birds being treated by rehabbers are reported to have desiccated and crusty eyes, ataxia (loss of body control), and general behaviors (tremors) atypical of healthy birds. Internal effects discovered during necropsy have not yet been reported.

Which states are experiencing this outbreak?

This map depicts the current known outbreak of afflicted birds in the eastern US.
This map will be updated with additional reports of symptomatic birds that match the current outbreak.

Currently, there are 10 states, and the District of Columbia, that are reporting birds with matching symptoms: West Virginia, Indiana, Ohio, Pennsylvania, New Jersey, Kentucky, Tennessee, Virginia, Maryland, Delaware, and Washington, D.C. If you reside in these states, the current recommendation is to take down your feeders or clean them daily. If you have a birdbath, leaving water out can help during these constant heatwaves, but keep the birdbath clean.

If the outbreak is tied to Brood X, states experiencing a hatch may want to be alert for birds exhibiting the symptoms listed above. States that may have Brood X cicadas present are New York, Michigan, Illinois, North Carolina, South Carolina, and Georgia. If you reside in these states, be prepared to take down your feeders or start cleaning them daily, however, if it is not disease-related, your feeders will have no impact. If this is an infectious disease, taking down feeders will help birds the most. If you have a birdbath, leaving water out can help during these constant heatwaves, but keep the birdbath clean.


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If this die-off is due to an unknown disease, birdwatchers in the surrounding region will want to be ready to take down feeders or boost their cleaning schedules to a daily regimen. If you live in these states, be prepared, but do not be alarmed. The states with potential risk are Wisconsin, Iowa, Missouri, Arkansas, Mississippi, Alabama, Florida, Connecticut, Rhode Island, Massachusetts, and Vermont.

What is Brood X?

Periodical cicada or Magicada cassinii specimen from Brood X
This detailed photo depicts a periodical cicada from Brood X. Photo credit: Anders Croft/USGS

Periodical cicadas are insects that belong to the order Hemiptera (true bugs). They feed on plant fluids (xylem) both below and above ground. Brood X (Brood 10) is the largest brood of the 17-year cicadas. There are currently 12 broods of 17-year cicadas and 3 broods of 13-year cicadas. Two broods have gone extinct (one near Connecticut and one in Florida).

This brood is found in three separate areas centering around Pennsylvania and northern Virginia, Indiana, and eastern Tennessee. The largest emergence of Brood X appears as adults once every 17 years. There are 7 species of periodical cicadas. There are also annual cicada species (that are green) that emerge annually.

The periodical cicadas begin to emerge the first or second week of May and are typically gone by the end of June. Annual cicadas, however, are present from June through August.

Want to see the most recent cicada brood years and maps? Check out this information offered from USFS.

What are the symptoms of pesticides in birds?

While some pesticides, like DDT, have an indirect effect during a single part of a bird's life cycle (DDT affected the eggshell of many bird species), others can have a more direct effect, killing birds quickly. Symptoms that can appear in birds (and other animals) include excess salivation, tearing, watery or excessive excretions, regurgitation, convulsions, lethargy, paralysis, tremors, blindness, and other neurological afflictions. Animals may also develop difficulty breathing and die due to paralysis of the respiratory muscles, and some organs may face complete failure as well. Additional potential symptoms include endocrine disruption, alterations in feeding behavior, and compromised immune systems which affect avian reproduction are also possible due to certain toxins.

How to help sick or injured birds

Most state wildlife agencies are calling for the removal, or constant cleaning, of bird feeders. However, if our speculation holds any water, this will do very little. To be safe during this time, we recommend following the recommendations of your local wildlife agency. If you find a sick bird, report it to your local wildlife managing agency and transport the bird to your nearest wildlife rehabilitation clinic!

Reports matching this current outbreak are beginning to subside, so further effort to help birds may not be necessary. Though, reports subsiding may also align with cicada swarms beginning to subside.


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