Allen's hummingbird Selasphorus sasin

Extremely similar to widespread Rufous Hummingbird; identical in plumage except for males' solid green back (which can be shown by Rufous too). Breeds only along a narrow strip of coastal California and southern Oregon. On females and immature males, the only way to separate them from Rufous is by the shape of the tail feathers, which is extremely difficult to determine without good photographs.