The Ruby-Crowned Kinglet has a ruby spot or stripe on the top of its head. It isn't always visible, but sometimes it really stands out. The little fella I saw today had the sun glistening off of his red mohawk. This isn't a picture of the bird I saw today, but it gives you an idea.
The other bird with a red spot today was a Downy Woodpecker. While the females have a pretty black and white pattern, the male has a bright red patch on the back of its head. On our bird walk in January we saw a female. I saw a male today along the creek. Very beautiful!