Looks at the adaptive significance of bird behavior. A lifetime spent in ornithological research and old-fashioned bird-watching has convinced the author that "we have consistently underestimated what goes on in a bird's head." He describes how using the latest available tools, neurobiologists have uncovered new aspects of bird perception--e.g., the fact that female birds that see in the ultraviolet range chose mates on the basis of characteristics we can't directly perceive such as plumage markings. Even more fascinating, Birkhead explains that some birds "tend to use their right eye for close-up activities like feeding and the left eye for more distant activities such as scanning for predators." Another unexpected discovery which he hopes may prove relevant to the treatment of neuro-degenerative brain disease in humans is the plasticity of the brains of birds that live in temperate regions.