Each spring, more than 80 percent of the world's population of sandhill cranes converge on Nebraska's Platte River valley - a critical sliver of threatened habitat in North America's Central Flyway. Cranes come to rest and refuel for a month as they prepare for the arduous journey to vast breeding grounds in Canada, Alaska and Siberia. They arrive from far-flung wintering grounds in northern Mexico, Texas and New Mexico on an epic journey of thousands of miles. Along with them come millions of migrating ducks and geese in the neighboring Rainwater Basin.

For centuries, they have come to rest and restore themselves. The shallow braided channels of Nebraska's Platte River provide safe nighttime roost sites. Waste grain in crop fields provides food to build up depleted fat reserves needed for migration. Adjacent wet meadows provide critical nutrients and secluded loafing areas for rest, bathing and courting. During their stop in Nebraska, cranes gain nearly 10 percent of their body weight.

Sandhill cranes are living dinosaurs. Fossils of wing bones dating back nine million years have been discovered in Nebraska. The species has survived because of its complex social behaviors, long term care of its young, innate wariness and adaptability.

Like all cranes, sandhill cranes mate for life. They typically lay two eggs per year, with one chick usually surviving the first year. A family of cranes will spend about three weeks along the Platte.

There is no question: The arrival of the cranes on the Platte River - and the millions of other migratory birds that visit each spring - is one of the greatest wildlife spectacles on the continent.