Identification Tips: Adult FEMALE Ruby-throated Hummingbirds

Bill: Long and thin.
Chin: The chin of hummingbirds are white.
Throat: Female Ruby-throated Hummingbirds have white throats – or gorgets – with light gray streaks.
Breast: Female Ruby-throated Hummingbirds have bright white and unmarked breasts.
Eye: Adult female Ruby-throated Hummingbirds have dark eyes. Interestingly, there is a bright white spot just behind the eye -- which in the right light can be noticeable.
Flanks and Underparts: The sides and underparts of the female Ruby-throated Hummingbirds are also yellow-green (not bright green) that also shimmer with a golden iridescence under certain sunlight conditions. Sibley Guides online offers a great explanation of the iridescence of hummingbirds.
Tail: The female Ruby-throated Hummingbird has a rounded tail (not sharply pointed like the male's tail feathers) with the outer three tail feathers having white tips. When perched, the tail is slightly longer than the male Ruby-throated Hummingbird.