Migration of Birds (1950)

A comprehensive survey explains why and how many bird species undertake seasonal movements, reviewing historical observations and competing ideas on origins and control, including ancestral-range shifts, photoperiodic cues, and continental changes. It outlines when and how birds travel, contrasting nocturnal and diurnal movements and detailing flight speeds, typical altitudes, navigation methods, and segregation by age or sex. Geographic coverage ranges from short local shifts to long-distance migrations and includes continental flyways, coastal and oceanic routes, vertical movements, and occasional vagrancy. The work examines hazards such as storms, exhaustion, and man-made obstacles, summarizes banding and observational studies, and highlights implications for conservation and management.