Spring is officially into its second week, and the signs are starting to show. Perhaps nowhere is this more true than along the North Platte River in Nebraska, where spring means the annual northward migration of hundreds of thousands of sandhill cranes, who stop at the river for the world's largest crane fiesta. The dancing, omnivorous, monogamous birds are the most populous of the planet's 15 crane species, nine of which are endangered.

The cranes stop each March [1] on an 80 mile stretch of the river - all that remains of a habitat that once spread for 200 miles until dams, power plants, and other development interfered. But despite their shrunken habitat, the cranes are thriving. If you can't make it to the great crane party, you can witness it live online via National Geographic's Cranecam [2] (you'll need RealPlayer, which you can download via a link on the site [3] ).

Audubon's Rowe Sanctuary [4], near Kearney, Nebraska, offers bird-watching trips and scores of facts about the cranes, one of the world's oldest species of bird, which have visited Nebraska for nine million years.

Photo credit: National Geographic Society [5]