...sapsuckers. All three used to be lumped as the single species Yellow-bellied Sapsucker. A couple of decades ago, the AOU Committee decided to split this bird based on genetic evidence. Typically, it's relatively easy in the field to distinguish the current three species: the throat pattern of the Red-naped, with its red throat that bleeds through the black lateral throat stripe; the extensive red on the head and breast of the Red-breasted, and the plain nape and irregularly mottled back of the Yellow-bellied. In addition, of course, range maps will help. But more and more sapsuckers are showing up out of range and showing intermediate plumages.
All of this makes me wonder whether we shouldn't stop trying to identify weird-looking sapsuckers in the field and instead take inspiration from the old species epithet of the combined Yellow-bellied group: varius.