As far as I know, and let's face it, that's not very far at all, your concept of what a REV looks like is in line with my interpretation. Obviously, the red-eye is a give-away, but that feature is not always highly visible in poor light. I tend to zero in on the gray skull cap and the superciliary arch detail (eye brow and eye brow liner). The Warbling vireo is very drab and lighter in overall colour with no dark accents, although the blue feet are a bit bold. The Philadelphia has a fair amount of soft yellow wash and a dark lore (between the eye and the base of the bill). I have not seen many warbling vireo this year, either in spring or now. Philadelphia and Red-eyed are abundant now. The mixed flock from this morning included Am. Redstart, Cape May, Common Yellowthroat and REV. The most striking feature of the vireos is that they will tolerate people more than warblers, and even warblers are not shy, and vireos will often come lower down, closer to ideal photo level and may even perch right beside me for an instant as if checking me out.
