A comparative approach to the study of communication can be seen as extremely valuable for a thorough understanding of human communication. In its broadest sense, communication is a biological phenomenon, defined as the interchange of information between an organism and its environment. Communication systems of living organisms differ qualitatively and in relation to their fundamental differences and environments. Moreover, they cannot be ranked on a superiority scale. Both cultural and noncultural factors may influence communication abilities and behavior. Although the formal rationalist method of investigation presented by Chomsky and Miller poses some problems, it can be applied in studying animal communication systems and does allow for the exploration of numerous possibilities. This procedure, followed in working with the common loon, has proved highly productive and has provided material for further study. (JM)