The Evolution of Diversity in Avian Territorial Systems

W HAT are the conditions which facilitate or hinder the evolution of territoriality? No generally accepted solution to this problem has yet been found-perhaps because too specific an answer has been sought for too general a question. Instead, the diversity of systems of territorial and other aggressive behavior has come to be well appreciated, as evidenced in recent reviews of territoriality (e.g., Kuroda, 1960; Carpenter, 1953; Hinde, 1956), and the impossibility of providin g a specific answer applicable to all types of territoriality is now realized. Arguments over which are the primary selection pressures leading to certain types of territoriality continue, however, as shown in the recent contributions bearing on the “function” of territoriality by Stenger (1958)) WynneEdwards (1962), Kalela (1958)) Kuroda (1960), Peters (1962)) and others. The present paper offers a new orientation to the problem by presenting a general theory for the evolution of territoriality with special reference to its diversity among species. Since most of the previous theories have already been shown to be untenable or severely limited (see especially Carpenter, 1958; Tinbergen, 1957; and Hinde, 1956, for criticism of them), little attention will be given to them here.