The past two decades have seen an explosion in our appreciation of the feats of endurance and complexity involved in bird migration - yet the science that informs these majestic journeys is still in relative infancy. Pulitzer Prize-shortlisted writer and ornithologist Scott Weidensaul embarks on a voyage of discovery which sees him sail through the storm-wracked waters of the Bering Sea; encounter gunners and trappers in the Mediterranean; and visit a corner of northeast India, where former headhunters have turned one of the grimmest stories of migratory crisis into an unprecedented conservation success.