While most people know that birds migrate, few know the extent and magnitude of this annual process that spans the globe, passing over wilderness and dense urban areas. Gulf Crossing is the story of one of North America's greatest natural phenomena: the yearly migration of billions of birds from the tropics to the northern forests and tundra, and back again. Guided only by their instincts for thousands of miles across the hemisphere, the heart of their journey is a non-stop 600 mile flight across the Gulf of Mexico.—Anonymous