A Critique of Interspecific Territoriality and Character Convergence

Abstract

Avian species may converge in appearance or voice because such convergence enhances mutual interspecific territoriality that results in the exclusion of food competitors. The cases presented in support of this convergence hypothesis do not link any case of convergence with any case of interspecific territoriality; hence, the hypothesis does not explain any real situation, much less a substantial body of fact. There exist cases of interspecific territoriality that are unexplained by the convergence hypothesis. These known cases indicate that mutual interspecific territoriality between species extensively coexisting in the same habitat is rare. They also indicate that interspecific territoriality occurs between species which occupy different habitats, forage outside their territories, and differ in appearance, voice or both. Finally, the predictions of the convergence hypothesis are contrary to the predictions of the Competitive Exclusion Principle.