Sandhill cranes (Grus canadensis) fly in to roost in the shallows of the Platte River. Every year 400,000 to 600,000 sandhill cranes—80 percent of all the cranes on the planet—congregate along an 80-mile stretch of the central Platte River in Nebraska, to fatten up on waste grain in the empty cornfields in preparation for the journey to their Arctic and subarctic nesting grounds. Sandhill cranes among the world's oldest living birds and one of the planet's most successful life-forms, having outlasted millions of species (99 percent of species that ever existed are now extinct); Wood River, Nebraska, United States of AmericaImage #: 34557519 See More From: Randy Olson