Year-round resident Anna's Hummingbird, Beaverton, Oregon, 6 November 2011 by Greg Gillson.
Even though I recently sang the praises of the new National Geographic Field Guide to the Birds (6th Edition), it didn't help with the identification of the hummingbird outside my window. Though I knew that the hummingbird was likely an Anna's Hummingbird, the NatGeo6 hasn't changed its artwork of Costa's Hummingbirds since the first edition. Frankly, this field guide doesn't help with the separation of female Costa's and Anna's Hummingbirds.
That's why I have many field guides, and specialty guides too. No book can be all things to all people. And even if one field guide was superior, there's nothing wrong with variety.
In his book, the Kaufman Field Guide to Advanced Birding, Kenn Kaufman has a chapter on hard-to-identify hummingbirds.
Perhaps because I rarely go to places with any hummingbirds but Rufous and Anna's, I've always had trouble with female hummingbirds of the Anna's/Costa's/Ruby-throated/Black-chinned type--in other words, hummingbirds that look very similar to the one depicted above.
So I spent some time recently observing the hummingbirds at the feeders outside my window. I practiced observing tail feather shape, facial pattern, and inner primary width--with the help of my camera. I feel a bit better prepared now in case some unexpected female hummingbird pops up (as they can do in the autumn of the year). Better prepared, yes, but I still would hope that a future rare hummer at my feeder will be an easier to identify male!
Map of winter range of Anna's Hummingbird in the Pacific NW based on eBird data.
A previous post on Anna's Hummingbirds.