In the past two decades, our understanding of the navigational and physiological feats that enable birds to cross immense oceans, fly above the highest mountains, or remain in unbroken flight for months at a stretch has exploded. Crossing the Pacific Ocean in nine days of nonstop flight, as some birds do, leaves little time for sleep, but migrants can put half their brains to sleep for a few seconds at a time, alternating sides—and their reaction time actually improves.These and other revelations convey both the wonder of bird migration and its global sweep, from the mudflats of the Yellow Sea in China to the remote mountains of northeastern India to the dusty hills of southern Cyprus. This breathtaking work of nature writing also introduces listeners to those scientists, researchers, and bird lovers trying to preserve global migratory patterns in the face of climate change and other environmental challenges.