Wading In: Introduction to Fish-Birds

In this introductory chapter, we explain why the first Europeans to encounter penguins at sea, back in the 1500s, were not all that far off in their opinion that penguins were some sort of fish or, for some, a combination of fish, mammal, and bird. Indeed, among aquatic air-breathing creatures, penguins are the best adapted to deal with the incredible physical challenges imposed by the sea. These include the density and viscosity of seawater, the unbelievable high pressures encountered at depth, the way water sucks heat out of warm-blooded animals, and the quickness and adaptability of their prey (real fish!). This chapter reviews the phylogenetic history of the current suite of penguin species, which had their beginnings 20 million years ago. We note that because penguins need to lay eggs and tend to their chicks on land, there was interspecific competition for land and water space, resulting in the evolution of size and shape differences and certain physical and physiological compromises that other air-breathing aquatic vertebrates have not needed to make. We review how oceanic climate, the volcanic rise of islands, and other factors, with many operating through interspecific competition, have affected penguin size. We list the population sizes of the current penguin species as well as summarize their physical attributes, such as size, wing shape, and extent of gender dimorphism.