Dr. George Barrowclough uses molecular data and computer analyses to investigate the evolution and systematics of birds. This research includes phylogenetic studies, as well as intraspecific studies of population genetics and phylogeography. The latter have included species such as the spotted owl and California gnatcatcher, which are of conservation concern. Traditional studies of geographic variation using plumage and skeletal measurements have been replaced by DNA surveys from population samples distributed across the range of species. These surveys allow the inference of both historical processes, such as range expansion and population growth, and continuing phenomena, such as gene flow and population interaction in hybrid zones.