"Avian vagrancy--the appearance of birds outside of their expected habitat--is a phenomenon that has fascinated natural historians for centuries, from Victorian collectors willing to spend fortunes on a rare specimen to today's bird-chasing "twitchers." Yet despite the obsessions of countless ornithologists, what do we actually know about the enigma of vagrancy? In Vagrancy in Birds, Alexander Lees and James Gilroy explore the causes, patterns, and...