Allen's Hummingbird, Selasphorus sasin

The back and crown on male Allen's Hummingbirds are green, as shown on the left (also note the ant in his bill!) The same areas on the similar male Rufous Hummingbird are rufous, sometimes with a few green feathers. (A very few Rufous males show an all-green back; an all- or mostly-rufous back is diagnostic of Rufous.)

Female Allen's and Rufous Hummingbirds generally can't be distinguished in the field by structure or plumage, except in the rare case where (as in the picture below) the tail feathers are visible. The Allen's second tail feathers out from the center (R2) are lanceolate (symmetrically spear-shaped) as can be seen  espcially clearly on this bird's left side in this picture. The same feather on the Rufous is notched on one side. This holds for both sexes in the two species. Female Allen's can also be identified when at the nest, by location; Allen's nest in coastal California, while Rufous only migrate through.

These Allen's hummingbirds were all photographed over a weekend in early April 2008, around Ruby-cluster bushes in the Australia section of the UC Santa Cruz Arboretum, probably the best place to see this species. Several of the males were performing the distinctive Allen's display flight -- a J-shaped ascent and dive, similar to the display of the male Anna's Hummingbird, following a "shuttle," in which the bird flies back and forth from side to side. The display flight of the male Rufous Hummingbird is elliptical, without the shuttle.