Allen’s hummingbirds are medium-sized birds with a slightly curved black bill. Males have plumage similar to that of the rufous species coupled with an iridescent green hue on the cap and back. The bib is bright red-orange, the chest is white with red on the sides of the belly and on the caudal covers.
The plumes of the thighs are white. Underwings are red-cinnamon below the tail and duller at the base. The legs are crepuscular.
Females have a metallic green-bronze top. Median and lateral rectrices have the same characteristics as in males. The external rectrices have a green and black subterminal band while external rectrices have white and black endpoints.
You will also notice a little velvety green. Brownish feathers are more or less tinged with purple. The lower parts have characteristics that are similar to the rufous.
Male juveniles have plumage similar to their mother except for the upper tail, which has an almost entirely red-cinnamon hue. The cinnamon throat is moderately mixed with bronze. The female and the juveniles are almost indistinguishable from the rufous hummingbirds. The sedentarius breed is bigger and heavier than the latter. Females have greener rectrices.
Allen’s hummingbird species do not sing during parades or deterrence rituals. At the end of the dive, these birds produce pure whistles different from those of the rufous hummingbirds. The dances are punctuated with small notes both chirping and buzzing.
During the nesting season, Allen’s hummingbird species are restricted to areas bordering the Pacific Ocean in California. They are particularly noticeable in the moist ravines and canyons at the top of the ridges.
At certain times of the year, males place a high preference for the territories that overlook the chaparral plots while their partners tend to frequent the willows and patches of blackberry scrub that lie at the bottom of small ravines or grow at top of the hilly slopes.
In the middle of the summer season, these birds sometimes visit the sierras.
The southern migration routes run along the top of the slopes of the hilly reliefs. In the Berkeley area, they follow the deep course of streams whose shores are abundantly adorned with vegetation. Non-migratory breeds live in island habitats with abundant vegetation and almost always travel the same route and often perform the same ritual.
Allen’s hummingbird species are territorial. There are generally two types of territories: feeding areas and nesting areas. The feeding areas are located in areas of scrub within which the males pursue intruders and initiate deterrence maneuvers.
These feeding areas are many but small in area and they are subject to small disputes. However, Allen’s hummingbirds only defend these hardwood areas and open spaces between three and 14 meters above them. As a result, interspecific encounters are not as frequent as does Anna’s hummingbirds. There are no aggressive conflicting encounters between different species.
On the other hand, the second kind of territory is used for the spectacular acrobatics, which take place a little before mating. The male climbs up the sky by following a curved trajectory then takes a long plunge until he reaches the position of the female. This kind of acrobatics is also common among hummingbirds in the southwestern United States.