CONTENTS 



CHAP. PAGE 



I. Migration of Biros 1 



Definition Variation of migration. 



II. Cause and Origin of Migration ... 13 



Direction of passage The potentiality of flight Habit 

 of wandering Memory Extension of range Influence 

 of Temperature Desire for Light Glacial Epoch Food 

 Basis Sexual Impulses Competition. 



III. Routes . ' 33 



Route or Broad Front Coasting Fly-lines Isepip- 

 teses Land-bridges Coast Lights. 



IV. The Height and Speed of Migration Flight . 47 



Altitude of Normal Migration Variation in Speed 

 Effect of Wind. 



V. Orientation and Route Finding ... 56 



Route Finding Use of Memory Eyesight Errors 

 Guidance of Young Beam Winds Homing of Terns. 



VI. The Distances Travelled by Birds 65 



The Swallow Variation in Distances Marking Birds 

 Results Routes of the Golden Plover Evolution of 

 the Routes. 



