Doug spotted this beautiful butterfly on one of our bushes this afternoon. I'm not knowledgeable about butterflies, but I submitted a photo of this one to http://www.butterfliesandmoths.org/. They got back to me shortly with the identification. It's a Red Admiral (Vanessa atalanta).
It's not a rare type of butterfly, by any stretch of the imagination; but we couldn't remember having seen one before. According to the information on the website, Red Admirals prefer sap flows on trees, fermenting fruit, and bird droppings; visiting flowers only when these are not available. Then they will nectar at common milkweed, red clover, aster, and alfalfa, among others.
I guess this one couldn't find any tasty bird droppings today.