These two look nearly identical at a glance. Both have a similar black-and-white pattern, same red patch on the males, but a few reliable differences hold up: - Size. Downy Woodpecker is small, roughly sparrow-sized. Hairy Woodpecker is noticeably larger, closer to robin-sized. - Bill length. This is the most reliable mark. Downy's bill is short and stubby, about half the length of its head. Hairy's bill is long and substantial, close to the full length of its head. - Outer tail feathers. Downy Woodpecker has small black spots along its white outer tail feathers. Hairy Woodpecker's outer tail feathers are clean white, no spots. The problem with this: Hairy Woodpeckers occasionally have spots on their tail too. (don't ask me why only some do, I have no idea!!) If you're at a feeder, size and bill length together will usually settle it without needing the tail feathers at all. Check out ways to separate more similar birds with Cheat Sheets in the Classroom tab: https://www.skool.com/better-birders-7312/classroom