Have you ever seen birds squabble at a feeder? Birds can be territorial around their food sources, and some always seem to come out on top. Using data from Project FeederWatch, researchers pieced together a hierarchy that ranks the feeder performance of 136 North American bird species. Here's a sample of what they found. You may be surprised by some of the rankings (think—the feistiness of a woodpecker or the docile nature of a goldfinch). Learn through the link below. Do you have a favorite in