This quiz shows warblers as they are so often seen in the field – with just the underside of the body visible. Clues such as tail shape, overall size, behavior and other subtleties can be very helpful with experience. In this quiz I focus on the more objective features of plumage.
When all you can see is the belly, flanks, and tail of a warbler, take note of tail pattern, any streaking, and the overall pattern of dark/light and bright/drab. You should be able to identify most species by matching those patterns to the pictures in the guide, and with practice you will recognize more and more warblers from these small clues.
With thanks, again, to Brian E. Small for providing the beautiful photos. You can see lots more at his website.