I endeavor to understand how the environment, geography, ecology, and evolutionary history influence biodiversity. In pursuit of this broad research goal, I take a comprehensive approach to natural systems, examining them at both inter- and intra-specific evolutionary timescales. Birds are an ideal study group to examine the processes producing biodiversity because they are morphologically diverse, use multiple signaling pathways (i.e., visual and auditory), often form hybrids, and possess genomes of tractable size. Avian systems thus provide a wealth of opportunity to examine the production and maintenance of biodiversity.