Allen's "Allen's Hummingbird"
A close relative of the Rufous Hummingbird, Allen's has a more limited range, nesting mostly in California. This is one of the two common nesting hummingbirds in northern California gardens (Anna's is the other). Females and immatures of Allen's Hummingbird are almost impossible to separate from Rufous females without close examination, so the status of the species in migration is still being worked out by dedicated hummingbird banders.
-National Audubon Society