Ruby-crowned kinglet
One of our winter songbird visitors is the tiny Ruby-crowned Kinglet. While the males do have a ruby-red crown feathers, they’re often hidden unless they are excited by a potential mate, rival or a predator. Personally, I’ve never actually seen a male flash his ruby-crown so I’m relying on other observers for this info. Other than this pop of color, the thin-billed Ruby-crowned Kinglet is normally a dull olive-green with a white eyeing and white bars on their wings.
These little birds seem quite nervous and constantly flip their wings, even when they are on the ground.