Tech tips for spotting birds -- and why we love to watch them

In spring, half a million sandhill cranes gather on the Platte River.
From mid-February to mid-April, half a million sandhill cranes gather along the Platte River. Emaciated when they arrive from Mexico and the southern U.S., they fatten up to migrate on to Minnesota, where some move on to sub-Arctic and Arctic nesting grounds.
Stephen Wilkes | National Geographic