The Magnificent Hummingbird was first named Rivoli's Hummingbird by René Lesson (in honor of the Duke of Rivoli) when he described the species in 1829 (Mearns and Mearns 1992a). Even when it became known that William Swainson had written an earlier description of this species in 1827, the name Rivoli's Hummingbird stuck until the early 1980s when it was changed to Magnificent Hummingbird.
The two races of this hummingbird inhabit a combined range that extends from the southwestern United States to Panama. The northern race (Eugenes fulgens fulgens), found from the southwestern United States to Nicaragua, is the most widely distributed of the two groups and is the second-largest hummingbird in the United States. The larger southern race (E. f. spectabilis) is found in Costa Rica and Panama. Both races exhibit sexual dimorphism, primarily in coloration, body mass, and bill length.
The Magnificent Hummingbird occurs primarily at mid- to high elevations throughout much of Mexico and Central America. Birds in the northern half of the species' range migrate north in early spring to breed, and some of them make it to a small region in the far southwestern portion of North America (primarily Arizona and New Mexico). Birds in the extreme southern portion of the range appear to be nonmigratory except for some movement to lower elevations after the breeding season. Throughout its range, the Magnificent Hummingbird occurs in a variety of habitats, but it is most frequently found in dry pine (Pinus)-oak (Quercus) forests. In North America, breeding appears to be confined to the riparian ravines found in the small mountain ranges of southern Arizona and New Mexico, where nests are often constructed high up in trees that overhang streams.
Despite this species' relative abundance, much remains to be learned about it, especially in the United States; most information comes from studies in central and southern Mexico and in Costa Rica. The transient nature of males and the secretive habits of females have discouraged U.S. studies, although it appears that northern males may forage more by traplining (see Behavior: agonistic behavior) than by being territorial and aggressive. Key questions regarding mating and courtship remain unanswered.