LINES OF MIGRATORY FLIGHT 141 



the coastal plain and Piedmont plateau east of the 

 Alleghany Mountains, those that come down the 

 broad reach of the Mississippi Valley, and many 

 that come south through the Plains region. Millions 

 of birds then cross the stretch of five to seven hun- 

 dred miles of open water across the Gulf of Mexico, 

 to reach southern Mexico, where there is land over 

 which they may continue to Central America or to 

 South America. The Isthmus of Panama offers a 

 narrow passage, but apparently many birds scorn 

 its protection and fly directly across the Bay of 

 Panama. I have seen barn swallows in such flight, 

 and have examined in the flesh a Traill's flycatcher 

 killed by striking a ship crossing this bay at night. 

 Hosts of warblers and others of our smaller birds 

 cross the Gulf of Mexico direct, and comparatively 

 few take the more roundabout channel through 

 Florida to Cuba and from Cuba to Yucatan, though 

 for many years this was assumed to be the regular 

 channel for our eastern birds that winter in eastern 

 Mexico. It seems simpler for the travellers to at- 

 tempt the direct journey in spite of the fact that on 

 the Cuban route it would be necessary to cross 

 barely one hundred miles of open water. 



In the northern portion of the broad central area 

 of North America there is a distinct trend of migra- 

 tion lines in spring toward the northwest (and in 

 autumn to the southeast), which carries many dis- 



