Yolo Bypass Wildlife Area, 45211 Co Road 32B, Davis, CA 95618, USA
The Yolo Bypass Wildlife Area is a nice place to take a drive through to see a lot of different birds. The number of different species of ducks you can see on a 20 minute drive is really amazing. They have more than just ducks though. You might be able to see different types of geese, swans, and other marsh birds.
Bring some binoculars and a bird book. The kids will enjoy using the binoculars looking at the brightly colored drake/male ducks. You don't really need the binoculars though. Most of the birds will be fairly close to you.
There's no entrance fee. When you enter the area, just follow the signs for the hunter check station.
Usually you'll be able to see the most birds during the late fall and winter months. That's when the waterfowl migration occurs.