During our Washington County, Ohio Big Day, the Whipple Bird Club was fortunate enough to see BOTH species of yellowlegs. Not only that, but as we were discussing the finer points of telling greater yellowlegs from lesser yellowlegs, the birds obliged by standing next to each other in perfect profile for a few moments.
This really gave us a good look at the key field marks: the differences in bill length and size; body size; leg length; and plumage markings on the flanks (of the greater).
It might make birding less challenging, but wouldn't it be great if more birds cooperated like this? I'm talking to YOU sharpies & Coops, scaups, peeps, empids, chickadees, shrikes, ibises (ibi?), and most of the dang sparrows!