Allen's hummingbird

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.

Allen's hummingbird is a small bird, with mature adults reaching only 3 to 3.5 in (76 to 89 mm) in length and weighing approximately 2 to 4 grams in weight. They are known for their vibrant colors and energetic behaviors, making them a popular subject for birdwatchers and nature enthusiasts. 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 male hummingbirds make use of their elaborate colors to impress the females, which is crucial for mating season. 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 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. The breeding seasons and ranges are common factors used to differentiate between the two species in a particular geographical area. Allen's hummingbirds breed mainly along coastal forests and shrub areas from California to Oregon.

Compared to other hummingbird species, the Allen's Hummingbird has a comparably shorter lifespan. They typically live between three and five years, with the oldest recorded Allen's hummingbird being at least 5 years and 11 months old.