My research uses a comparative approach to investigate the roles of geological and climatic events in the buildup of biodiversity and promotion of the latitudinal diversity gradient. To address biogeographic questions I combine phylogenetic analysis across multiple taxonomic groups with field experiments, museum work and simulation studies. Current projects investigate: 1) how rates of speciation, extinction and morphological and behavioral evolution vary across latitudinal gradients in Asian and New World birds, 2) the role of Great American Biotic Interchange in promoting an excess of biodiversity in the New World tropics, 3) the role of historical climate changes in accelerating evolution and extinction and 4) utility of avian molecular clocks.