Scientists baffled by hundreds of sick and dying birds across the U.S.

Hundreds of birds are dying without explanation in parts of the South and Midwest.

Wildlife experts in at least six states and Washington, D.C., have reported an increase in sick or dying birds in the past month. The most commonly afflicted birds are blue jays, common grackles and European starlings.

“We’re experiencing an unusual amount of bird mortality this year,” said Kate Slankard, an avian biologist with the Kentucky Department of Fish and Wildlife Resources. “We have yet to figure out what the problem is. The condition seems to be pretty deadly.”

Symptoms include crusty or puffy eyes, neurological signs of seizures and an inability to stay balanced.

Experts said the birds have been behaving as if they are blind and exhibit other abnormalities, such as not flying away when people get close.

“They’ll just sit still, often kind of shaking,” Slankard said. “It’s pretty safe to say that hundreds of birds in the state have had this problem.”

In addition to Kentucky and D.C., Ohio, Indiana, Maryland, Virginia and West Virginia have reported similar deaths, officials said.

“We’re all working together as a multistate group to try to figure out what’s going on,” Slankard said. “Diagnosing these problems is complex because several rounds of lab tests must be done.”

Some theories about what's causing the birds to become sick and die include a widespread infectious disease, the cicada outbreak and pesticides, said Laura Kearns, a wildlife biologist with the Ohio Division of Wildlife. She said hundreds of birds have been found dead in the state.

Indiana wildlife officials said there have been suspicious deaths of blue jays, robins, northern cardinals and brown-headed cowbirds in five counties. James Brindle, spokesman for the state's Department of Natural Resources, said birds there have tested negative for avian influenza and West Nile virus.

The bird specimens from Kentucky were sent to the Southeastern Cooperative Wildlife Disease Study at the University of Georgia for testing.

“This is probably a new issue,” Slankard said of what’s possibly causing the deaths.

In September, New Mexico wildlife experts said birds in the region were dropping dead at an alarming rate, potentially in the hundreds of thousands, NBC News reported.

Scientists were baffled by the deaths. Officials said they aren’t sure if the two events are related.

Wildlife experts are asking the public to report any suspicious bird deaths. They also urge bird lovers to remove their bird feeders since birds often exchange germs.

Bird feeders and baths should also be cleaned immediately with a 10 percent bleach solution, and people should avoid handling birds, officials said.