Penguins are the world's most easily recognized--and perhaps most appealing--group of birds. Flightless, penguins spend the vast majority of their lives swimming in the sea, yet they cannot shake off their evolutionary past: they are warm-blooded air breathers, and they must return to land to lay their eggs. Thus penguins face the challenges of balancing two worlds--the land for breeding, the sea for feeding. This engaging book offers a complete and up-to-date overview of all the world's penguin species as well as new insights into their dual lives. The book shows that the diversity of penguin species, and in fact all aspects of their biology, can be explained largely according to the distance they travel for food. Exploring penguin colonies, social behavior, evolution, ecology, conservation issues, and more, the book provides a fascinatingly detailed portrait of these unique and popular birds.