Great Horned Owl (Bubo virginianus) - HBW 5, p. 185

Taxonomy: Strix virginiana J. F. Gmelin, 1788, Virginia.
Has sometimes been considered to belong to the B. bubo superspecies. Formerly included B. magellanicus as a race, but DNA, voice and morphology found to differ. Numerous geographical races named, many poorly differentiated, or apparently result of individual variation, or due to wandering birds from other parts of range: thus, forms described from coastal W Alaska (algistus), C Canada (scalariventris), Venezuela (scotinus), E Colombia (elutus), C Colombia (colombianus) and E Brazil (deserti) considered not acceptable; also, name occidentalis used for birds from Rocky Mts of WC Canada to WC USA, but now synonymized with subarcticus; older name wapacuthu formerly applied to populations of W & C Canada and N USA (limits uncertain), but validity questioned; in addition, N populations lagophonus and heterocnemis possibly not separable from saturatus, perhaps better merged with latter; boundaries of races often obscure, and problem further complicated by birds of intermediate appearance; races pacificus and pallescens intergrade in California. Pending further study, twelve races tentatively recognized.