 of the great crane migration. Every winter, thousands of sandhill cranes fly to Merced National Wildlife Refuge in California's San Joaquin Valley. Thousands of acres of wetlands provide these cranes with a natural source for food and shelter. Maintaining these wetlands is crucial for their survival. Watching these majestic cranes with up to seven foot wingspans is one of nature's most breathtaking sights. If you're not already into bird watching, you will be after you see these big birds.