Contents 



Page 



The mystery of migration 4 



Advantages of migration 6 



The origin of migration 7 



Northern ancestral home theory 8 



Southern ancestral home theory 8 



Theory of photopcriodism 9 



Theory of continental drift 11 



When birds migrate 11 



Movements of species and groups 12 



Nocturnal and diurnal migration 15 



How birds migrate 18 



Speed of flight and speed of migration 18 



Altitude at which birds travel 26 



Orientation 28 



Segregation during migration 31 



Where birds migrate 34 



Short and undetermined migrations 34 



Variable migrations within species 35 



Fall flights not far south of breeding ranges 37 



Long-distance migrations 38 



Routes of migration 41 



Wide and narrow migration lanes 42 



The fly ways 46 



Atlantic oceanic route 48 



Atlantic coast route and tributaries 53 



Mackenzie Valley-Great Lakes-Mississippi Valley Route and tributaries 60 



Great Plains-Rocky Mountain routes 62 



Pacific coast route 63 



Pacific oceanic route 66 



Arctic routes 68 



Evolution of migration routes 70 



Vertical migration 72 



Vagrant migration 73 



Perils of migration 75 



Storms 75 



Aerial obstructions 76 



Exhaustion 78 



Influence of the weather on migration 80 



Problems of migration 81 



Banding studies 81 



Movements of residents 82 



Migration of the white-throated sparrow 84 



Migration of the yellow-billed loon 84 



Conclusions 85 



Appendix I — List of birds mentioned in the text 87 



Appendix II — Bird banding 92 



Bibliography 94 



Index 99 



III 



