The Davis Causeway between Sac and Davis is home to trillions of bats. Every night, ten minutes after sunset one or two bats decide to start their hunt for mosquitoes, grass hoppers and other like insects. All the other trillion bats follow that one bat out in "ribbons" .. it is a site to see!!! don't miss out! The best months to do this is june july and august. There are tours. Do not wash your car before hand (it is very dusty there). Do bring wine and cheese or chocolate and beer (just don't show it to the cops:) pay attention to the lunar phase and catch it when the moon is rising full or sliver! Enjoy your Northern California summer evenings!
I stumbled on this phenomenon on my many motorcyle trips to that part of town. If I timed my rides wrong, My helmet's face shield would be full of bugs and insects. So now I time it so that the bats beat me to the feeding grounds first then I take that liesurely ride home though clean face screen.
also a great activity after a Davis bike ride (and farmer's market) or before hitting the city night life.
this is just a bonus: wilderness survival skill that I had to use one evening under that bridge waiting for better timing. Enjoy!