French documentarian Luc Jacquet casts the annual breeding migration of Antarctica's emperor penguins as an operatic struggle between stoic every-birds and the cruel gods of wind, ice and 24-hour darkness who test their battered but steadfast souls. Frankly, they don't need the hard sell: The penguins' matter-of-fact victory over some of the Earth's most punishing conditions is astonishing enough without the epic airs. The handsome emperors, some 3-foot-6 inches tall and weighing between 45 and 90 lbs. — much of it insulating blubber — are a model of evolutionary specialization. But the adaptations that make them living rockets underwater — dense, furlike feathers; f...