Orange-crowned Warbler (Oreothlypis celata) are named after a feature that I've never seen in the wild. They have an orange patch on the crown of their heads that's typically hidden. They are another Winter bird for me, and often forage in the same areas as Ruby-crowned Kinglets, eating bugs, berries, and bits of flowers where they find them. I was following a Kinglet around when this guy came along. Males and females look very similar, but females' colors are more muted - this is the more brightly colored male.
I hear these birds far more than I see them, since they forage amid the foliage of brushy areas where their soft green/yellow colors are pretty effective camouflage. They have a distinct high pitched chip sound, and the males have a lovely song. While they forage down low, when it's time to sing, the males will fly up high in a tree to better project their songs.
This shot is a little soft (left the camera at f/10 and a slow shutter speed from shooting some pond scenes - curses!), but I was pretty happy to manage to finally get a photo of one of these birds after seeking them out for a good while.