I like to read accounts of wildlife written by early settlers of California, like this one: “A gunshot would send so many waterfowl into the air that they would darken out the sun for minutes.”
We still can experience awe-inspiring sights during migration. In fall and spring we can watch thousands of birds migrating low over the ocean. In fall, you can visit Hawk Hill in Marin County where Golden Gate Raptor Observatory keeps records of migrating hawks as they fly in a slow spiral, waiting to catch updrafts that will carry them across the bay. Some 4,000 Red-tailed Hawks have been recorded this fall, with reports of 19 per hour.
This fall, I strongly encourage you to visit the Sacramento National Wildlife Refuge, a part of which is located next to Interstate 5. Here you can see hundreds of thousands of geese, swans, ducks and even Sandhill Cranes and their young.
The entire trip is made worthwhile in the one moment when thousands of Snow Geese take to the air with a cacophony of flapping wings and cackling calls. It is a taste of what the entire Central Valley autumn was like before the arrival of humans.