Ruby-crowned Kinglet

Small migratory bird which can be mistaken for a Hutton's Vireo. The Hutton's will have two white bars with a dark line between and the Ruby-crowned would have two white bars with lower one being bolder and a dark line below the lower bar. These birds also have eye ring that is thicker in front and behind. Color is an Olive on back and wings and greyish underneath. Bill is short and pointed.
Males have a small red patch on the crown, but usually not seen much. I've seen it when the bird is irritated.