Just a few days after thousands of blackbirds fell from the sky in Arkansas, about 500 birds dropped to their death in Louisiana, littering a stretch of highway near Baton Rouge.

Biologists are trying to figure out what killed the birds in rural Pointe Coupee Parish, La. Nearly 500 kilometres to the north, in the small town of Beebe in central Arkansas, scientists said celebratory fireworks on New Year's Eve likely sent thousands of discombobulated blackbirds into such a tizzy that they crashed into homes, cars and each other before plummeting to their deaths. Officials acknowledged it's unlikely they'll ever pinpoint a cause with certainty.

A worker collects dead birds from the backyard of a home in Beebe, Ark., on Jan. 2. (Stephen B. Thornton/Arkansas Democrat-Gazette/Associated Press)

In Beebe, New Year's revellers spent the holiday weekend cleaning up between 4,000 and 5,000 dead red-winged blackbirds. Some speculated that bad weather was to blame. Others said one confused bird could have led the group in a fatal plunge. A few spooked schoolkids guessed the birds committed mass suicide.

"There was probably some physical reason, but I doubt anyone will ever know what it was," said Thurman Booth, the state's wildlife services director.

The birds were the second mass wildlife death in Arkansas in recent days. Last week, about 83,000 dead and dying drum fish washed up along a 20-mile stretch of the Arkansas River, about 100 miles west of Beebe. Wildlife officials said the fish deaths are not related to the dead birds, and that because mainly one species of fish was affected, it is likely they were stricken by an illness. Full test results could take up to a month.

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.

Birds rained from sky

While the bird carcasses are examined for signs of disease and the contents of their stomachs are tested for toxins, the tale of the blackbirds' tumble is quickly turning into the stuff of local legend.

The blackbirds rained onto rooftops and sidewalks and into fields. One struck a woman walking her dog. Another hit a police cruiser. Some say an umbrella was one resident's only protection from the falling birds.

Red-winged blackbirds are among the most abundant birds in North America, with a population estimated at 100 million to 200 million. (David Zalubowski/Associated Press)

Birds were "littering the streets, the yards, the driveways, everywhere," said Robby King, a county wildlife officer in Beebe, a community of 5,000 about 60 kilometres northeast of Little Rock. "It was hard to drive down the street in some places without running over them."

A few stunned surviving birds stumbled around like drunken partiers.

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.

"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."

Shane Roberts said it sounded like hail pelting his house.

"I turn and look across my yard, and there's all these lumps," Roberts said.

His 16-year-old daughter, Alex, spent Saturday morning picking them up with her bare hands.

"Their legs are really squishy," she said.

For some people, the scene unfolding shortly before midnight evoked images of the apocalypse and cut short New Year's Eve celebrations. Many families phoned police instead of popping champagne.

"I think the switchboard lit up pretty good," said Beebe police Capt. Eddie Cullum. "For all the doomsdayers, that was definitely the end of the world."

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 Duke, a suspension supervisor at a nearby school.

A few dead birds still littered town streets Monday.

The birds will not be missed in the community. Large roosts like the one at Beebe can have thousands of birds in one tree that leave ankle- to knee-deep piles of droppings in places.

"The whole sky turns black every morning and every night," Roberts said, as a few live birds chirped and hopped from tree to tree behind his home.

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. Rowe put the number of dead in Beebe at "easily 3,000."

Massive trauma

The Game and Fish Commission shipped carcasses to the Arkansas Livestock and Poultry Commission and the National Wildlife Health Center in Madison, Wis. Researchers at the University of Georgia's wildlife disease study group also asked for a set of birds.

A few grackles and a couple of starlings also were among the dead. Those species roost with blackbirds, particularly in winter.

"They died from massive trauma," said Game and Fish Commission spokesman Keith Stephens, citing a report from the state poultry lab where the birds were examined.

Residents heard loud fireworks just before the birds started hitting the ground.

"They started going crazy, flying into one another," Stephens said.

The area where the birds fell is too large to determine if any specific blast rousted the birds, police Chief Wayne Ballew said.

"It was New Year's Eve night. Everybody and their brother was shooting fireworks," the chief said.

The city allows fireworks only on New Year's Eve and Independence Day.

Bad weather has been blamed for earlier bird kills in Arkansas.

In 2001, lightning killed dozens of mallards at Hot Springs, and a flock of dead pelicans was found in the woods about 10 years ago, Rowe said. Lab tests showed they, too, had been hit by lightning.

In 1973, hail knocked birds from the sky at Stuttgart, Ark., on the day before the start of hunting season. Some of the birds were caught in a violent storm's updrafts and became encased in ice before falling from the sky. Some were described as bowling balls with feathers.

Earlier Friday, a tornado had killed three people in Cincinnati, Ark., about 240 kilometres away, but most of the bad weather had passed Beebe when the birds died.

Rowe initially said poisoning was possible but unlikely. Birds of prey and other animals, including dogs and cats, ate several of the dead birds and suffered no ill effects.

"Every dog and cat in the neighborhood that night was able to get a fresh snack," Rowe said.