 This ecologically catholic neotropical songbird provides perhaps one of the clearest and most widely distributed habitat-related dialect systems.The geographic variation in the song of this species became apparent over 30 years ago with F. Nottebohm's study in subtropical and temperate Argentina.He interpreted his findings largely in the context established a few years before in the white-crowned sparrow, that is, he suggested that these dialects perhaps serve to enhance the genetic integrity of local populations.