Drivers were pulling over to the side of the road along Highway 16 in East Sacramento County to see what was going on.
Jeff McLeod was one of several people who pulled over to look at the thousands of birds swarming.
"At first, it looks like a funnel cloud," he said.
While it may look bizarre to us, the birds are practicing a common behavior. Experts say it's all part of an evening routine they do before going to sleep.