Dead birds falling from sky still mystify experts

Scientists still don’t know what’s causing flocks of birds to drop from the sky in the South, even as several hundred more fell dead onto a Louisiana highway.

The puzzling phenomenon started on New Year’s Eve when thousands of blackbirds were found dead in central Arkansas. Townsfolk spent their holiday weekend removing the remains of between 4,000 and 5,000 dead red-winged blackbirds. Scientists have descended on the town, trying to find a cause for the mass die-off.

In the latest incident early this week, some 500 birds were discovered scattered on a rural road in Louisiana's Pointe Coupee Parish, 300 miles south of the Arkansas site. Officials there are stumped as to what caused the birds to plunge to their death.

Wildlife officials in both states were sending carcasses to researchers at the National Wildlife Health Center in Madison, Wis., and the University of Georgia. No one is yet connecting the two mass deaths, but the Audubon Society is closely monitoring the situation.

“Mass bird die-offs can be caused by starvation, storms, disease, pesticides, collisions with manmade structures or human disturbance,” says Greg Butcher, Audubon’s director of bird conservation. “Scientists are still investigating what happened to the birds in Louisiana and Arkansas, but initial findings indicate that these are isolated incidents that were probably caused by disturbance and disorientation.”

The birds that died –- red-winged blackbirds, common grackles, brown-headed cowbirds and European starlings –- are abundant species that flock together in large nighttime roosts during the winter months. Roosts can contain from tens of thousands to 20 million individuals or more, according to Audubon.

The U.S. Geological Service's website lists about 90 mass deaths of birds and other wildlife from June through Dec. 12. Five list deaths of at least 1,000 birds and another 12 show at least 500 dead birds.

The largest was near Houston, Minn., where about 4,000 water birds died between Sept. 6 and Nov. 26 from infestations of various parasites.

Red-winged blackbirds are among North America's most abundant birds, with somewhere between 100 million and 200 million nationwide, according to the Cornell Lab of Ornithology in Ithaca, N.Y.

-- Julie Cart