Page Introduction 1 Mystery of migration 3 Historical accounts 3 Advantages of migration 4 Theories of causes of migration 5 When birds migrate 7 Movements of species and groups 8 Nocturnal and diurnal migration 11 How birds migrate 13 Speed of flight andspeed of migration 13 Altitudes at which birds travel 22 Orientation 23 Segregation during migration 25 Where birds migrate 27 Distances of migration vary 27 Short and undetermined migration 27 Variable migrations wi thin species 28 Fall flights not far south of breeding ranges 29 Long-distance migrations 30 Routes of migration 33 Wide and narrow migration lanes 34 Atlantic oceanic route 39 Atlantic coast route and tributaries 42 Mackenzie Valley-Great Lakes-Mississippi Valley route and tributaries 45 Pacific coast route 47 Pacific oceanic route 49 Arctic routes 52 Evolution of migration routes 52 Vertical migration 55 Vagrant migration 55 Perils of migration 56 Storms 56 Aerial obstructions 57 Exhaustion 59 Influence of the weather on migration 59 Problems of migration 61 Banding studies 61 Movements of residents 62 Migration of the white-throated sparrow 63 Migration of the yellow-billed loon 63 Conclusions 65 Bibliography 66 Index 69 =INTRODUCTION=