Thousands of blackbirds that plummeted to their deaths in front of horrified New Year revellers in a small Arkansas town may have been stressed by fireworks.
The red-winged blackbirds rained out of the darkness on to rooftops and pavements and into fields as people in Beebe were enjoying midnight fireworks.
One struck a woman walking her dog and another hit a police vehicle.
Birds were "littering the streets, the yards, the driveways, everywhere", said Robby King, a county wildlife officer in Beebe, a community of 5,000 located north east of Little Rock.
"It was hard to drive down the street in some places without running over them."
For some people, the scene evoked images of the apocalypse and cut short New Year celebrations. Many families phoned police instead of popping champagne.
"I think the switchboard lit up pretty good," said Beebe police captain Eddie Cullum. "For all the doomsdayers, that was definitely the end of the world."
In all, more than 3,000 birds tumbled to the ground. Scientists said last night that the fireworks appeared to have frightened the birds into such a frenzy that they crashed into homes, cars and each other. Some may have flown straight into the ground.
"The blackbirds were flying at rooftop level instead of treetop level" to avoid explosions above, said Karen Rowe, an ornithologist with the Arkansas Game and Fish Commission.
"Blackbirds have poor eyesight and they started colliding with things." But Ms Rowe stopped short of declaring the mystery solved, saying labs planned to test bird carcasses for toxins or disease.
Another theory was that violent thunderstorms might have disoriented the flock or even just one bird that could have led the group in a fatal plunge to the ground.
A few stunned birds survived their fall and stumbled around like drunken revellers.
There was little light across the countryside at the time, save for the glimmer of fireworks and some lightning on the horizon. In the tumult, many birds probably lost their bearings.
"I turn and look across my yard, and there's all these lumps," said Shane Roberts, who thought hail was falling until he saw a dazed blackbird beneath his truck.
Paul Duke filled three five-gallon buckets with dead birds on New Year's Day. "They were on the roof of the house, in the yard, on the sidewalks, in the street," said the school supervisor.
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, New York.
Ms Rowe put the number of dead in Beebe at "easily 3,000".
The Game and Fish Commission shipped carcasses to the Arkansas Livestock and Poultry Commission and the National Wildlife Health Centre in Madison, Wisconsin.
Researchers at the University of Georgia's wildlife disease study group also asked for a set of birds. Test results could be back in a week.