One of the smallest and most colorful hummingbirds in North America, the male Broad-billed Hummingbird has a bright reddish bill, a dark green body and a brilliant blue gorget that set it apart from other hummingbirds found in the United States. The species ranges from the southwestern United States to southern Mexico. Sexual dimorphism is pronounced, particularly in body coloration.
In Mexico most Broad-billed Hummingbirds are resident, but in late spring and summer many individuals migrate to extreme northern Mexico, portions of southeastern Arizona, southwestern New Mexico, and the Big Bend region of southwestern Texas to breed. In these areas breeders inhabit riparian zones of arid canyons, usually below 2,000 m, which contain sufficient resources to support nesting for up to 5 months. Breeding behavior of females is typical of other hummingbirds except that nests are constructed low to the ground and rarely decorated with lichen. Little is known about the breeding behavior of males, although courtship is believed to involve a dynamic display.
Like other hummingbirds, the Broad-billed acquires the bulk of its energy from floral nectar produced by a large number of diverse wild and cultivated plants. These birds are probably opportunistic with regard to flower preference, but will select flowers with a high energy reward when given a choice. In the United States, nectar supplies in natural habitat vary greatly, and it is likely that peaks in nectar production lead to increases in reproduction.
Little is known about the social behavior of this species. Only a few observations have been made of its displays and vocalizations, and the function and importance of these activities remain unknown. Broad-billed Hummingbirds do interact with a number of other hummingbird species, and seem to adapt well to a variety of positions within a dominance hierarchy, as shown by their ability to use different foraging strategies depending on which other hummingbird species are present.
Compared to other hummingbirds in North America, the biology of the Broad-billed remains poorly studied, perhaps because its range is largely restricted to remote areas. Most of what is known comes from studies done in central Mexico that focused on habitat choice, social dominance, foraging behavior, and energetics ( Des Granges 1978 , Montogmerie 1979 ), and from Baltosser's ( Baltosser 1986a , Baltosser 1989b , Baltosser 1996 ) work on habitat choice, nesting ecology, and food availability for females. Gaps in our understanding of this species offer many opportunities for further study.