OUR GREATEST TRAVELERS 



347 



map showing the; principal routes used by birds in their migrations 



between north and south america 



ence to another, and not the distance 

 from one food base to the next. The 

 location of plenty of suitable provender 

 having been ascertained, the birds pay 

 no attention to the length of the single 

 flight required to reach it. 



PRINCIPAL MIGRATION ROUTES OE NORTH 

 AMERICA 



The shape of the land areas in the 

 northern half of the Western Hemisphere 

 has tended to great variations in migra- 

 tory movements. If the whole area from 

 Brazil to Canada were a plain with the 

 general characteristics of the middle sec- 

 tion of the Mississippi Valley, the study 

 of bird migration would lose much of its 

 fascination. There would be a simple 

 rhythmical swinging of the migration 

 pendulum back and forth spring and fall. 

 But a large part of the space between 

 Brazil and Canada is occupied by the 

 Gulf of Mexico, the Caribbean Sea, and 



parts of the Atlantic Ocean, all devoid 

 of sustenance for land birds. The two 

 areas of abundant food supplies are 

 North America and northern South 

 America, separated by the comparatively 

 small land areas of Mexico and Central 

 America, the islands of the West Indies, 

 and the great stretches of foodless 

 waters. 



The different courses taken by the 

 birds to get around or over this inter- 

 vening inhospitable region are almost as 

 numerous as the bird families that trav- 

 erse them, and only some of the more 

 important ones are shown on the accom- 

 panying map (page 347). The routes 

 are numbered from the east westward, 

 the middle one, No. 4, being by far the 

 most important. In general it may be 

 said to extend from northwestern Flor- 

 ida and western Louisiana across the 

 Gulf of Mexico to the southern coast of 

 the Gulf (Yucatan to Vera Cruz), and 



