Residents in the small city of Falköping found the dead Western Jackdaw birds lying scattered on a street in their neighborhood.
"Some had been run over, some were still alive," Sebastian Djurberg, who discovered some of the birds, told Swedish Radio news. "They lay still; they appeared shocked. They just lay there, waiting to die."
The cause of death is being investigated. To rule out possible poisoning and illness, several of the birds have been sent for testing at the National Veterinary Institute. The local district has collected the rest to cremate.
The leading theory is that they birds were scared by fireworks and even run over, according to county veterinarian Robert ter Horst.
"The main line of inquiry we're working with is that the birds either flew themselves to death or were scared to death. I've also received information that a driver ran over a number of the birds," said ter Horst.
According to local police some of the birds had been hit by cars but many of the birds had no visible injuries. The area where the birds were found is close to a recycling center, and police have now blocked off the area so a veterinarian could examine the birds and collect samples.
In the US state of Arkansas thousands of dead birds were found on the ground just before midnight on New Year's Eve, according to newspaper Dagens Nyheter. Authorities there believe that the birds where killed by stress caused by all the fireworks or a storm in the area.