Allen's hummingbird (Selasphorus sasin) is a species of hummingbird that breeds in the western United States. It is one of seven species in the genus Selasphorus. Description Allen's hummingbird is a small bird, with mature adults reaching only in length. The male has a green back and forehead, with rust-colored (rufous) flanks, rump, and tail. The male's throat is an iridescent orange-red. The female and immature Allen's hummingbirds are similarly colored, but lack the iridescent throat patch, instead having a series of speckles on their throats. Females are mostly green, featuring rufous color only on the tail, which also has white tips. Immature Allen's hummingbirds are so similar to the female rufous hummingbird, the two are almost indistinguishable in the field. The lack of a notch in the second rectrix (R2) is considered an important field mark to distinguish the adult male Allen's hummingbird from rufous hummingbird, particularly the hard to distinguish green-backed variety. Both species' breeding seasons and ranges are common factors used to differentiate between the two species in a particular geographical area. Taxonomy Allen's hummingbird was formally described by the French naturalist René Lesson in 1829 and given the binomial name Ornismya sasin. The specific epithet is a Wakashan or Nootka Native American name for a hummingbird. The type locality is San Francisco. Allen's hummingbird is now placed in the genus Selasphorus that was introduced by William Swainson in 1832. The common name commemorates Charles Andrew Allen, an American collector and taxidermist who identified the bird in 1879 in Nicasio, California. Two subspecies are recognised: S. s. sasin (Lesson, R, 1829) – breeds south Oregon and California (USA), winters in south central Mexico S. s. sedentarius Grinnell, 1929 – islands off south California (USA) A hybrid between this species and Anna's hummingbird has been described as Floresi's hummingbird, "Selasphorus" floresii. Distribution Allen's hummingbird is common only in the brushy woods, gardens, and meadows of coastal California from Santa Barbara north, and southern coastal Oregon. The nominate race, S. s. sasin, is migratory, and in southern central Mexico. A second, S. s. sedentarius, is a permanent resident on the Channel Islands off southern California. This population colonized the Palos Verdes Peninsula of Los Angeles County in the 1960s and has since spread over much of Los Angeles and Orange Counties, south through San Diego County, and east to the western end of Riverside County. Behavior The courtship flight