Some 500 dead and dying birds fell onto a Louisiana highway on Monday, just three days after a similar incident in Arkansas.
The events have led to speculation running from poisonings to "End of Days" scenarios, but a key federal agency emphasized that mass bird die-offs are not that rare.
Most of the birds found on Louisiana Highway 1 near Point Coupee were red-winged blackbirds, as was the case in Beebe, Ark., some 360 miles away. The species is one of the most common in the United States, with a population estimated at up to 200 million.
Some of the Louisiana birds will be tested by the National Wildlife Health Center run by the U.S. Geological Survey. But a USGS spokesman told The Baton Rouge Advocate that USGS records showed 16 incidents in the last 30 years where more than 1,000 blackbirds have died all at once.
"These large events do take place," he said. "It's not terribly unusual.".
The National Audubon Society agreed that mass bird die-offs are not rare. "Initial findings indicate that these are isolated incidents," Greg Butcher, Audubon's director of bird conservation, said in a statement.
The Louisiana Department of Wildlife and Fisheries also weighed in, saying that necropsies on some birds indicated many "exhibited traumatic injuries." The birds might have flown into nearby power lines, it added.
In Arkansas, preliminary tests showed the blackbirds there, as many as 5,000, died after massive trauma. Experts said the birds were likely spooked by fireworks, lightning or some other loud event and then ran into each other and other objects as they fled at night while roosting.
"The birds suffered from acute physical trauma leading to internal hemorrhage and death," the Arkansas Game and Fish Commission said in a statement Monday. "There was no sign of chronic or infectious disease."
The birds were otherwise healthy, according to the statement.
The injuries were primarily in the breast tissue, with blood clotting and bleeding in the body cavities.
