The Blue-throated Hummingbird is a fairly large hummingbird, reaching 11.5 to 12.5 cm (4½ to 5 inches) in length and 6 to 10 grams in weight. The Blue-throated Hummingbird is dull green on the top of its body, fading to medium gray on its belly. It has a conspicuous white stripe behind its eye and a narrower stripe extending backward from the corner of its bill, bordering a blackish cheek patch. Its tail feathers are iridescent blue-black with broad white tips on the outer two to three pairs. The species gets its name from the adult male's iridescent blue throat patch (gorget), but the female lacks this, having a plain gray throat. Males sing two types of songs: a simple "peep song," which sounds like a squeaky wheel, and a quiet but complex "whisper song." The female is also reported to sing during the breeding season to attract the attention of males.
The Blue-throated Hummingbird is native to mountain woodlands of Mexico, although during the summer it is an uncommon to rare resident of moist, wooded canyons in the Madrean sky islands of southeastern Arizona, southern New Mexico, and western Texas in the United States and northeastern Sonora, Mexico. A few individuals traditionally winter at feeding stations in southeastern Arizona.
The male takes no part in nest building or care of the young. The female constructs her nest from soft plant fibers, held together and attached to its support (a tree branch, flowering plant, fern, vine, rock shelf, or manmade object such as a wire or nail) using strands of spider silk stolen from spider webs. The exterior is camouflaged with green mosses where available; in drier habitats, mosslike dendroid lichens may be used, or the exterior may be left bare. Blue-throated Hummingbirds frequently nest over water, especially flowing streams. The two white eggs hatch in 17 to 19 days, and the young leave the nest at 24 to 26 days of age. Up to three broods per year are possible under ideal conditions; the female usually builds each new nest atop the previous nest, leading to nest "towers" at traditional nest sites.
Like other hummingbirds, the Blue-throated Hummingbird feeds on nectar from flowers and catches insects in flight and by gleaning from vegetation. In winter, sap from wells drilled by sapsuckers may substitute for nectar.