45 



dant that it now is, wintered in enormous numbers in the 

 Chesapeake Bay region and in the spring folhjvved the line of 

 the Great Lakes northwestward for more than a thousand miles 

 to breed in Alberta. No duck has a northwest-southeast migra- 

 tion more marked than that of the Scaup. In the winter, it is 

 to be found in greatest abundance near the Atlantic Coast from 



The relation of duck migration to the distribution of Potamogeion crispus 

 in North America. 



The range of P. crispus is shown by the black circles. In the East the small 

 circles represent the general range of the plant, rather than individual localities, 

 while the larger circles in the West mark the locations from which the isolated 

 western collections were taken. The direction of the migration routes of the 

 Canvasback and the Scaup are shown by the dotted arrowlines. 



Chesapeake Bay to Massachusetts; but in the spring, generally 

 following the chain of lakes from Ontario through to the Great 

 Slave, it moves to a breeding ground that extends from North 

 Dakota to Great Slave Lake, Sitka, and the entire length of the 

 Aleutian Chain. 



These birds are among the most voracious pondweed eaters. 

 The figures given by McAtee in the paper mentioned above are: 



