The first comprehensive coverage of a subject that has fascinated natural historians for centuries. Avian vagrancy is a phenomenon that has fascinated natural historians for centuries. From Victorian collectors willing to spend fortunes on a rare specimen, to today's high-octane bird-chasing 'twitchers', the enigma of vagrancy has become a source of obsession for countless birders worldwide. Vagrancy in Birds explores both pattern and process in avian vagrancy, drawing on recent research to answer a suite of fundamental questions concerning the occurrence of rare birds. For each avian family, the book provides an in-depth analysis of recent and historical vagrancy patterns, representing the first comprehensive assessment of vagrancy at a global scale. The accounts are accompanied by hundreds of previously unpublished images featuring many of the most exceptional vagrants on record. The book synthesises for the first time everything we know about the subject, making the case for vagrancy as a biological phenomenon with far-reaching implications for avian ecology and evolution.