Wait, Why Are They Called "Ruby-crowned" Kinglets?

Want a challenge? Try to photograph a Ruby-crowned Kinglet (Regulus calendula). They are brazen little birds, willing to get right in your face if you intrude into their territory, but they never seem to stop moving.

Want a real challenge? Try and capture why they are called "Ruby-crowned" Kinglets. The males have a red patch on their head, and if they are really upset about something, it can be raised, but that happens rarely in my experiences so far. But today I managed to catch a couple of shots so you'll know what to look for on your own attempts!