What Killed the Blackbirds in Arkansas and Louisiana?

After approximately 5,000 blackbirds fell from the sky on New Year's Eve in Beebe, Ark., local authorities have been narrowing down the possible causes for this seemingly supernatural event as autopsies of the birds continue.

On Monday (Jan. 3), 17 of the red-winged blackbirds underwent necropsies, or animal autopsies. Carried out by the Arkansas Livestock and Poultry Commission Veterinary Diagnostic Lab, the necropsies' preliminary testing showed that they died after massive physical trauma.

Further tests will be done to rule out other causes, but the birds suffered from acute physical trauma leading to internal hemorrhage and death. There was no sign of any chronic or infectious disease, the report stated. The trauma that killed them was found to be primarily in breast tissue, with blood clots in the body cavity and internal bleeding.

Otherwise, the birds were the picture of health. The results ruled out poisoning, because the birds' gizzards and stomachs were empty, and their major organs were in normal condition.

As for what caused the blunt trauma, authorities theorize that loud New Year's Eve fireworks startled the birds from their roost and, because they have poor night vision, they flew into buildings.

"It's important to understand that a sick bird can't fly," Karen Rowe, an ornithologist with the Arkansas Game and Fish Commission, told Time.com. "So whatever happened to these birds happened very quickly. Something must have caused these birds to flush out of the trees at night, where they're normally just roosting and staying in the treetops ... and then something got them out of the air and caused their death and then they fell to earth."

Another possibility is that the birds were struck by stormy weather while flying at high altitudes. Such an occurrence isn't rare, and the birds' trauma points to the possibility that "the flock could have been hit by lightning or high-altitude hail," Rowe said.

Further necropsies and testing will be conducted on 50 additional blackbird samples at the National Wildlife Health Center lab in Wisconsin, with final results and the official cause expected to be released by the end of the month.

As the Arkansas birds were undergoing necropsies , another 500 dead birds, including blackbirds, starlings and sparrows, were found dead along a road in Louisiana, just 300 miles from Beebe. The two events, however, are most likely unrelated. The Louisiana birds appear to have died after the flock flew into a power line, with many of the birds suffering broken backs and beaks. What drove the birds to fly into the power line, however, remains a mystery.

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