PERILS OF MIGRATION 58 



Storms 58 



Aerial Obstructions 58 



Exhaustion 59 



ROUTES OF MIGRATION 61 



General Considerations 61 



Flyways and Corridors 62 



Narrow Routes 65 



Converging Routes 65 



Principal Routes From North America 69 



Atlantic Oceanic Route 69 



Atlantic Coast Route and Tributaries 70 



Mackenzie Valley-Great Lakes-Mississippi Valley Route 



and Tributaries 73 



Great Plains-Rocky Mountain Routes 75 



Pacific Coast Route 76 



Pacific Oceanic Route 80 



Arctic Routes 80 



PATTERNS OF MIGRATION 82 



Loops 82 



Dog-legs 87 



Pelagic Wandering 90 



Leap-frogging 90 



Vertical Migration 91 



Pre-migratory Movements 91 



Vagrant Migration 92 



ORIGIN AND EVOLUTION OF MIGRATION 95 



WHERE WE STAND 100 



BIBLIOGRAPHY 102 



LIST OF BIRD SPECIES MENTIONED IN TEXT . , . 115 



IV 



