MERCED COUNTY — A white cloud of mostly Ross's geese fly near a windmill and tractors last week near the Merced National Wildlife Refuge. The migrating birds are plentiful as they make the refuge their winter home. The refuge encompasses 10,258 acres of wetlands, native grasslands, vernal pools and riparian areas. It has the largest wintering populations of lesser sandhill cranes (20,000) and Ross's geese (60,000) along the Pacific Flyway. They mingle with thousands of other visiting waterfowl and shorebirds to make the refuge a true winter phenomenon. The refuge can be reached by driving eight miles south of Merced on Highway 59 and then eight miles west on Sandy Mush Road.