Northern South America is a hotspot of biological diversity and endemism in various groups, including birds. Thus, understanding the factors promoting high diversity in this region is central to biogeography and macroecology. Although some studies focused on understanding environmental factors associated with global patterns of diversity have revealed strong effects of contemporary climate and energy availability on such patterns, some have had limited success in predicting species richness in montane areas, where many range-restricted species are concentrated. Because present-day diversity reflects not only contemporary and local conditions but also historical and regional processes, the high diversity of birds in the Neotropics birds may be partly explained by high opportunities for evolutionary diversification. Therefore, an adequate understanding of tropical biodiversity requires a link between ecology and evolutionary biology to consider mechanisms promoting species coexistence as well the influence of processes of speciation, extinction, and dispersal. In this talk I will present examples of my studies on biogeography, and speciation of Neotropical vertebrates to illustrate historical processes that may have led to their high diversity, focusing on analyses testing whether evolutionary differentiation of populations may be caused by changes in migratory behavior and breeding seasons. In addition, I will explore two little-explored mechanisms that may partly account for replacement of related species along elevational gradients, one of the factors accounting for high beta diversity in tropical mountains: (1) competition mediated by parasites and (2) constraints on the structure and function of bird eggs.