Allen's Hummingbird (Selasphorus sasin) is a common hummingbird that breeds in coastal California and southwestern Oregon (U.S.A.) and winters mainly in Mexico, although it is found casually in winter along the Gulf Coast of the southeastern United States. The population on California's Channel Islands and the nearby mainland is nonmigratory. This is one of the two common nesting hummingbirds in northern California gardens (the other being Anna's Hummingbird, Calypte anna). This species is closely related to the Rufous Hummingbird (Selasphorus rufus), its more northern and more broadly distributed counterpart. Females and immatures of these two species are nearly impossible to distinguish in the field, but adult males can usually be distinguished by back color (typically solid green in Allen's and mostly rufous in Rufous).
Breeding Allen's Hummingbirds are found in wooded or brushy canyons, parks, gardens, and mountain meadows. In general, this species seems to have adapted fairly well to moderately developed residential areas. In their wintering range in Mexico, Allen's Hummingbirds are found mainly in foothill and mountain forests. They frequently feed at red tubular flowers. The nest site is typically on a horizontal or diagonal branch in a tree or shrub, generally low but sometimes up to 27 m above the ground. The nest, built by the female alone, is a neatly constructed cup of moss and plant fibers held together with pieces of spider web and lined with fine plant down, The outside is camouflaged with pieces of lichen. Old nests may be repaired and re-used. The clutch of two white eggs is incubated by the female alone for 17 to 22 days; the female is also solely responsible for feeding the young after hatching.The nest reportedly stretches as the young birds grow. Age at first flight is around 22 to 25 days.
Male Allen's Hummingbirds exhibit a J-shaped courtship display flight: flying high, diving steeply with a metallic whine at the bottom of the dive, then curving up to hover at moderate height. This is often preceded by a back-and-forth pendulum-like flight in front of the female.
(Kaufman 1996; AOU 1998)
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