The greatest challenge for Cultural Selection Theory lies is the paucity of evidence for structural mechanisms in cultural systems that are sufficient for adaptation by natural selection. In part, clarification is required with respect to the interaction between cultural systems and their purported selective environments. Edmonds et al. have argued that Cultural Selection Theory requires simple, conclusive, unambiguous case studies in order to meet this challenge. To that end, this paper examines the songs of the Rufous-collared Sparrow, which seem to (...) exhibit cultural adaptations minimizing signal degradation relative to local environments. Specifically, the more forested the habitat, the more the tail end of the song resembles a whistle rather than a trill; yet, variation in song is uncorrelated with genetic variation. This paper explores the mechanisms responsible for these putative acoustic adaptations through a series of computer simulations. The main point of this research is not to test this model, but to demonstrate that models of this type have the resources to meet the in-principle objections that have been raised against Cultural Selection Theory. This research lends much-needed empirical support to Cultural Selection Theory by clarifying the nature of the interaction between culture and environment. It also contributes to evolutionary theory by clarifying the scope and limits of adaptation by natural selection. (shrink)