The Black-chinned Hummingbird is found from southern British Columbia throughout most of the western United States and much of central and northern Mexico (Figure 1). Occurring from below sea level to elevations above 2,500 m, the species inhabits a variety of habitats ranging from lush urban settings to xeric desert washes, the latter being more typical of the habitat occupied by Costa's Hummingbird (Calypte costae). As a breeding species, it is most abundant in southern segments of its range, particularly in riparian habitats of southern Arizona and southern New Mexico, where linear stretches often support nests spaced approximately every 100 m.
There are few superlatives to describe the Black-chinned Hummingbird, as it is not the smallest or largest of North American hummingbirds, not the most colorful, nor is it the only species to occur within a region. The species is not special in the sense of having a limited and narrow distribution and there is little if anything unusual about its habitat requirements. The Black-chinned Hummingbird is most noteworthy for being rather generalized, occurring in a variety of settings, and for its abundance; these characters result in the species being of particular interest to research and conservation efforts.
Virtually everything that is known about the Black-chinned Hummingbird has come from studies of the species in the United States. Information on a population of smaller individuals confined primarily to Mexico (see Systematics: geographic variation, below) is practically nonexistent. Separation of female-plumaged Black-chinned from Ruby-throated (Archilochus colubris) hummingbirds has traditionally been upon the basis of measurements, but measurements of the southern population of the Black-chinned Hummingbird overlap entirely with those of the Ruby-throated (see Systematics, below).
Banding studies in southern Arizona have shown that thousands of Black-chinned Hummingbirds migrate through this area annually, many individuals following the same migration path as in previous years, and that many survive for longer periods than once thought. The species is highly adaptable, occupying urban residential areas and new habitats created after extensive alterations, and is readily attracted to feeders.
Few studies have specifically focused on the Black-chinned Hummingbird. Even in many comprehensive studies of hummingbirds, limited data are provided, and these are often presented as a basis upon which to compare species such as Anna's Hummingbird (Calypte anna). The following published works are noteworthy with respect to the data they provide on the Black-chinned Hummingbird: identification— Banks and Johnson 1961 ; Short and Phillips 1966 ; Lynch and Ames 1970 ; Stiles 1971a ; Baltosser 1987 ; Newfield 1992 ; Pyle 1997c ; vocalizations— Rusch et al. 1996b ; color discrimination— Goldsmith and Goldsmith 1979 ; life history, ecology, distribution, and status— Bené 1946 ; Pitelka 1951a ; Stiles 1973 ; Copenhaver and Ewald 1980 ; Ewald and Rohwer 1980 ; Norton et al. 1982 ; Ewald 1985 ; Baltosser 1986a ; Ewald and Bransfield 1987 ; Baltosser 1989b ; Brown 1992c ; Baltosser Baltosser 1995 , Baltosser and Scott 1996 ; physiology and metabolism—Lasiewski Lasiewski 1963 , Lasiewski 1964 ; Lasiewski and Lasiewski 1967 ; Hainsworth 1973 ; Calder III and Hiebert 1983 ; Powers and Conley 1994 .