Research interests include higher level phylogenetics of birds, studies of speciation and species status, and the description of patterns of geographic variation. These investigations are based on skin measurements, plumage color analysis, skeletal measurements and analyses, anatomical dissections, and molecular studies. Additional research involves biogeography of remote areas and life history studies of poorly known taxa. Staff members organize expeditions annually to areas throughout the world.

The Department of Ornithology maintains and curates one of the largest collections of bird specimens in the world. The research collections of the Department number nearly one million specimens; these include skins, skeletons, alcoholic preparations, eggs, nests, and tissue samples for molecular biochemical studies. A large number of type specimens and rare or extinct species are also found in its collections. The specimens represent all continents and oceans and nearly 99 percent of all species.