Vocal communication is central to the coordination of social behavior in many vertebrate species, and it has been particularly well studied in songbirds, which use their songs in different contexts to convey information about the singer or its environment (Catchpole and Slater 2008; Alger et al. 2016). While it is widely accepted that the songs of oscine passerine birds (the songbirds) have two main social functions: intrasexual competition, and courtship (Catchpole and Slater 2008), the evolution of large and complex song repertoires remains an evolutionary puzzle (Byers and Kroodsma 2009). The question is: why do some songbird species produce an elaborate vocal repertoire, while other species carry out courtship and competition with a far smaller and simpler repertoire? In this thesis I examine the adaptive value (social function) of song in malemale competition with an eye toward understanding how intrasexual selection may have driven the elaboration of the male Bachman’s sparrow (Peucea aestivalis) vocal repertoire. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection