The Blue-throated Hummingbird is the largest hummingbird found north of Mexico. The male weighs up to 10 grams, more than 3 times the weight of the familiar Ruby-throated Hummingbird (Archilochus colubris). This veritable giant among northern hummingbirds is also one of the most ecologically selective, preferring the edges of montane conifer forests in the highlands of Mexico and the shady understory of deciduous streamside forests in the “sky island” mountain ranges of the southwestern United States. The male's high-pitched, monotonous peeps are a signature sound of summer along rare perennial streams in the mountain canyons of southeastern Arizona, southwestern New Mexico, and western Texas.
Humans are drawn to the same riparian habitats favored by this species, and wherever people share its haunts, the Blue-throated Hummingbird builds its nests on houses, sheds, bridges, and other artificial supports. Like most hummingbirds, it is readily attracted to flower gardens and sugar-water feeders, a fact exploited by generations of ornithologists, birders, photographers, and other enthusiasts visiting its southwestern strongholds. Its large size and highly aggressive nature usually place this species at the top of the hierarchy at feeding stations, as well as at natural nectar sources. Artificial feeding may have helped northern members of this species survive winters in its high-elevation habitat; a few individuals are now year-round residents at feeding stations in Arizona, far from the known northernmost limit of the species' permanent range in northwestern Mexico.
Relatives in the same genus as the Blue-throated Hummingbird, the Amethyst-throated Hummingbird (Lampornis amethystinus) and the mountain-gems, inhabit the higher elevations of the mountains of Mexico and Central America. Though most of these species share the conspicuous facial markings of the Blue-throated, their plumage typically shows a higher degree of sexual dimorphism, more extensive iridescence, and more subtle markings on the tail. Although the Blue-throated Hummingbird is not as gaudy as many hummingbirds, its vocalizations are unusually complex; these vocalizations, combined with the boldly contrasting marking on face and tail, may substitute for the bright colors and aerobatic displays of some other hummingbirds. Males of the Blue-throated and some of its relatives utter complex songs during the breeding season. Even more unusual among hummingbirds is the complex song of the female Blue-throated.
The Blue-throated Hummingbird's large size, assertive behavior, and relative accessibility have made it a frequent subject for behavioral, ecological, and physiological studies ( Lasiewski and Lasiewski 1967 , Lyon et al. 1977 , Pimm 1978 , Kuban and Neill 1980 , Pimm et al. 1985 , Schuchmann 1985 , Rosenzweig 1986 , Powers and McKee 1994b ). Basic natural-history studies cover nesting, feeding, and molt patterns of populations in Mexico (Wagner Wagner 1946a , Wagner 1952b , Wagner 1954 , Wagner 1957a ), as well as vocalizations ( Ficken et al. 2000 ).