For more than 3,000 miles from the mouth of the Mackenzie to 

 the delta of the Mississippi this route is uninterrupted by 

 mountains. In fact, the greatest elevation above sea level is less than 

 2,000 feet. Because it is well timbered and watered, the entire region 

 affords ideal conditions for its great hosts of migrating birds. It is 



Density Line 



Representing Approximately 



3.000 Birds 



Figure 20. Principal migratory routes of the canvasback. The major route of travel 

 extends from breeding areas in central Canada southeast across the Great Lakes and 

 either south down the Mississippi River or east to Chesapeake Bay (After Stewart 

 et al 1958). 



74 



