Elizabeth and I drove through the Central Valley on our way to the Klamath Mountains today. The farmland was so flat, the roads were perfectly straight and named after letters in the alphabet.

We were on Road Z. At one point, the road’s pavement just ended and turned into gravel. There were no other cars around for miles.

It’s late November and all the fields were brown and yellow, separated by rows of trees with fall colors. Rain clouds billowed to the west over the Coast Ranges and to the east over the Sierra Nevada, but the sky was placid above us.

We were going to spend the night in Weaverville, but we amused ourselves on the way by visiting wildlife refuges in the Central Valley. One of our stops was the Gray Lodge Wildlife Area.

On the way there, we saw a group of parked cars with people milling about nearby. What were they doing? Was it an accident? We slowed down. Everybody had big binoculars hanging from their necks. They even had a scope on a tripod. These were birders—serious ones. Elizabeth rolled down her window and asked if they were looking at anything unusual. “Sandhill cranes,” one of them said, “about 200 yards west of the road. Nothing unusual, but something good to see.”

We stopped our car and got out. All I had was an old pair of pocket binoculars. I felt embarrassed looking through them. I could barely see the cranes.

Fortunately, the birders let us use their scope. The sandhill cranes were nearly four feet tall. They were slender and gray with bright red crowns. We heard their high-pitched rattling calls. Elizabeth watched a pair dance. A few cranes took off and circled gracefully before returning to the group. Then we thanked the birders and left for the wildlife area.

The Gray Lodge Wildlife Area is directly north of the Sutter Buttes. Known as the smallest mountain range in the world, the Sutter Buttes form a perfect circle of hills rising directly out of the Central Valley. They aren’t particularly tall, but the immense flatness that surrounds them ensures that they are often visible from hundreds of miles away. I’d seen them many times while driving Interstate 5.

Gray Lodge Wildlife Area was the closest I’d ever been to the Sutter Buttes. They were right in front of me. But now they were completely obscured by low, gray clouds.

We did the gravel auto tour route through the refuge. The landscape started out pleasant enough: a mix of brush, tall cottonwoods, and marshes. The wetlands were filled with ducks, geese, and other birds. Nice.

Things got better when the clouds cleared a little. It was late in the afternoon and the sunlight came in at a low angle. It lit up the yellow and umber leaves of the trees next to the marshes. I could finally make out the western hills of the Sutter Buttes. Their grasslands were gold and the oaks and pines scattered upon them were dark green spots.

Storm clouds were piling up over the Sierra Nevada. Thousands of white geese were flying past the clouds, illuminated by the setting sun. They were far enough away to look like dots, but there were so many that they turned into an endless stream of white Vs crossing the sky.

The white geese were snow geese and Ross’s geese. They’re both big white fowl with black wingtips. They’re similar enough that I couldn’t tell them apart. But because of their colors, their silhouettes alternate distinctively between black and white as they flap their wings.

Near the end of the auto tour we passed one last wetland backed by the Sutter Buttes. It was filled with ducks and geese, much like the others. We stopped our car, rolled down our windows, and turned off the engine. The only sounds were wind, honking geese, and flapping wings.

Then the sound of a distant plane startled the birds.

The geese lifted up from the water in one giant wave. They blocked the view of the buttes behind them. Their white bodies and black wingtips made the entire mass flicker light and dark. Geese kept lifting up from the water, filling in the mass, as the others climbed higher. They filled the sky above us, swirling in different directions. There were thousands upon thousands of them.

I thought of the old accounts of endless herds of bison on the American prairie, how they once stretched to the horizon. And I thought of the old accounts of passenger pigeons, how their flocks could at one time darken the sky for days. Even California’s Central Valley once sustained some 40 million waterfowl on nearly 4 million acres of wetlands. Today, only 400,000 acres of wetlands remain. Waterfowl populations, predictably, have fallen to a tenth of what they once were. I wondered: If we could see so many birds on the wildlife area’s puny 9,200 acres, what was the entire Central Valley once like? I imagined the birds returning from their summer breeding grounds in the Arctic only to find the wetlands they had used for thousands of years drained and plowed. Starvation, disease, or hunting finished them off. It made me sad to think of the abundance that was once commonplace and of the millions of animals that had been sacrificed for wealth. The geese we saw were a reminder of what had been lost and what our land could still support.

We drove away. Dark clouds closed in. Rain pelted the roof our car. The Sutter Buttes faded behind the downpour. The huge flocks of birds we saw were no longer visible, vanished into the air.