Emperor penguins cross a treacherous frozen sea to reach their breeding grounds, and on the way one becomes lost in a blizzard. Rockhoppers brave the world's stormiest seas, only to come ashore and face a daunting assault up a 300-foot cliff, hopping most of the way up. Humboldts are a strange tropical penguin that has rarely been filmed. To reach their desert nests they negotiate 20,000 predatory sea lions, dodge vampire bats and battle half a million sharp-beaked seabirds. Among the spy cameras capturing unique behaviour is a technological first - robotic penguins with cameras for eyes.