Dr. Capparella is involved in a variety of research efforts involving fieldwork in South America and the United States. Most of his work focuses on the historical diversification of birds in South America. His dissertation, "Effects of riverine barriers on genetic differentiation of Amazonian forest undergrowth birds", argued that avian evolutionary development has been influenced by a little-studied geographical feature, the rivers of the Amazon region. In addition to new avian species, Capparella and Millikin colleague, Tom McQuistion, have discovered new parasites in South American birds. A comparative study of organochlorine pesticide contamination of neotropical and North American migrant passerines is also underway.

Glyphorynchus spirurus
castlenaudii