Just before midnight Tuesday, residents of Falkoping found 50 to 100 jackdaws dead on a street. The bizarre incident echoed similar cases in the United States.
Public veterinarian Robert ter Horst said the birds may have been frightened by fireworks Tuesday night and then run over.
"We have received information from local residents last night. Our main theory is that the birds were scared away because of the fireworks and landed on the road, but couldn't fly away from the stress and were hit by a car," he told The Local Wednesday.
"We will continue to look at whether there are other theories, but then we have to do an autopsy on the birds. The birds just now are in a car on the way to a laboratory in Uppsala," Ter Horst added.
The site has been closed off for an examination of the birds.
Anders Wirdheim of the Swedish Ornithological Society said the jackdaws probably were frightened in the middle of the night, then flew around in the dark and collided with objects.