An exploration of the causes and patterns of avian vagrancy 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 processes behind the occurrences of these unique birds. Lees and Gilroy draw on recent research to answer fundamental questions: What causes avian vagrancy? Why do some places attract so many vagrant birds? Why are some species more predisposed to long-range vagrancy than others? The authors present readers with everything known about the subject, and bring together different lines of evidence to make the case for vagrancy as a biological phenomenon with important implications for avian ecology and evolution. Filled with a wealth of photographs, Vagrancy in Birds will fascinate avian enthusiasts everywhere.