NSSome of these species are also found in Quebec.
Scientists are still trying to pinpoint the problem, but young people appear to be most at risk.
The USGS, which coordinates responses to some natural disasters, recommends that people remove bird feeders and baths temporarily to reduce the number of places where birds can congregate and potentially infect themselves.
Which birds are affected?
So far, the majority of affected birds have been the chicks of blue jays, American robins, starlings, and blackbirds, but other songbirds have also been affected.
The most prominent symptoms are puffy eyes or a dry discharge around the eyes, as well as an imbalance that may indicate neurological damage.
Why are birds sick?
In late April and May, officials were first notified of the presence of sick birds in Maryland, Virginia, West Virginia, Kentucky and Washington, DC. The information now comes from Pennsylvania, Delaware, New Jersey, Ohio and Indiana.
The outbreak may have peaked in June and started to subside in some places, but it’s continuing in others, according to Brian Evans, an avian ecologist at the Smithsonian National Institute of Conservation and Garden Biology.
What causes disease?
Specialists are still searching. By testing sick and dead birds, they determined that outbreaks were not primarily caused by viruses such as salmonella, chlamydia, bird flu, West Nile virus, or some other virus that regularly infects birds.
What can I do to help?
US officials recommend removing feeders in backyards, avoiding handling of sick birds, and keeping pets away from birds. It is also recommended to disinfect birdbaths with a solution of 10% bleach and 90% water.
“Because we don’t know what it is, we have to be more vigilant. We still don’t know if it’s caused by a virus or bacteria” or a toxic product in pesticides, said Jordan Rutter, a spokesman for the American Bird Conservation Organization, Jordan Rutter.
Mr. Rotter suggests replacing the feeders with native plants that provide food, such as berries and nectar, which will also attract insects that birds eat.
How unusual is this outbreak?
Birds are susceptible to many viruses and bacteria. When an infectious pathogen begins to spread in an area, officials usually recommend people remove feeders outdoors.
In the spring, the spread of salmonella among songbirds in several states prompted the US Centers for Disease Prevention and Control to keep up with that recommendation.
The difference this time is that scientists do not know the cause of the disease.