CHAPTER V 



General Observations on Lines of 

 Migratory Flight 



FROM previous statements it will be realized 

 that there is infinite variety in the distances 

 travelled by various birds in migration, and in the 

 choice of the routes that are followed. In fact, the 

 variety is so great that it almost seems as if the 

 methods employed in migration by no two species 

 exactly coincide. One species travels farther than 

 another, one passes south and another southwest, 

 one begins migratory movement early and another 

 procrastinates, and so on in a highly varied assort- 

 ment of differences. There are factors, however, 

 that tend to throw floods of migration along certain 

 lines and to leave other areas occupied to a less de- 

 gree, so that there are certain general lines of migra- 

 tion that may be traced. 



Much has been written about these paths of mi- 

 gration, and it is generally recognized that birds in 

 migratory flight tend to follow lines of major topo- 

 graphic relief on the earth's surface when these 

 trend in the proper direction. Lanes of migration 



