Why Penguins Communicate: The Evolution of Visual and Vocal Signals is a comprehensive and condensed review of several hundred publications on the evolution of penguin behaviors, particularly signaling, linking genetics and ecology via such behavioral adaptations as nuptial displays. This exciting work has developed from the authors' many years researching on the behavioral strategies of penguins, such as the unique vocal signatures for individual recognition. Studies of penguins on islands surrounding Antarctica are presented, fully showcasing the behavioral significance of visual ornaments (mating displays) and how and why penguins behave via adaptive evolutionary explanations. Through this evolutionary lens, the authors address several questions involving their identification and taxonomy, habitat and location, breeding, and differences between penguins and other seabirds. Each species occupies a unique ecological niche, and behaviors permit separating the species through mutual display. Although model organisms in science are diverse and specialized, we see the entire integration in penguins, from acoustical and optical physics, to behavioral display and speciation. This work highlights the adaptive significance of their behavior through an evolutionary point- of-view.