For several weeks, cars parked in Windsor Avenue, Littleover, Derby, have had their paintwork scratched and windscreen wipers broken.
It was assumed humans were responsible - until two crows were spotted attacking vehicles.
"It's a pair of nesting, territorial crows that are seeing their reflection in vehicles' bodywork.
"As far as they are concerned, it is another rival crow and they are attacking it.
"They develop a behaviour called referred aggression."