Every spring they come...A half million of them. Most of the sandhill cranes on this earth. And for a long, splendid month in March and early April they live and dance along the Platte River north of Minden, Neb. There may be a whooping crane among them, traveling along to Arctic nesting grounds. Togeher, these maginificent birds represent one of nature's most unforgettable spectacles. At sunrise the old railoroad bridge a mile north of Fort Kearny is the ideal place to watch the cranes. Plan on arriving a half-hour before sunrise and staying a half-hour after sunset. Seats and parking are plentiful. Another good location for watching the cranes leave and come back to the roost is the south bridge over the Platte River on Highway 10--park your car just south of the bridge. During the day, the cranes feed in the cornfields along Highways 50 and 10. It's important that you stay in your car to watch the birds as thry are extremely wary of persons on foot. Located 10 miles North of Minden.