442 Cooke, Bird Migration in the Mackenzie Valley. Loct. 



BIRD MIGRATION IN THE MACKENZIE VALLEY. 



BY WELLS W. COOKE. 



The Mackenzie Valley in northern Canada presents a broad sur- 

 face with a gentle slope rising only eight hundred feet in the fifteen 

 hundred miles from the mouth of the Mackenzie to the head of 

 steamboat navigation on the Athabaska at Fort McMurray. The 

 height of land between it and the valley of the Saskatchewan to 

 the south is but slightly over two thousand feet in elevation and 

 presents an almost uniform flat surface with not even a ridge of 

 hills to mark the change of slope from the north to the south. 



The migratory birds of the Mackenzie Valley have the choice of 

 three principal routes as they return from their winter homes. 

 They can come from the south, through Alberta, western Saskat- 

 chewan, western Montana and Utah, where Great Salt Lake, the 

 winter home of thousands of birds, lies directly south of Great Slave 

 Lake. A second route passes up the Pacific coast of the United 

 States to Washington and thence up the valley of the Columbia to 

 the headwaters of the Athabaska or up the valley of the Fraser to 

 the watershed of the Peace River. The third route is up the Miss- 

 issippi River to southern or central Minnesota ; thence to the valley 

 of the Red River of the North and up the Assiniboine and Saskat- 

 chewan Rivers to the sources of the Athabaska in Alberta, or across 

 Saskatchewan at right angles to the valleys of these rivers directly 

 to Lake Athabaska. 



The first of these routes 4ies across a wilderness of mountains 

 with many divides 8,000 to 10,000 feet high, and in the southern 

 half of the United States through a district largely a desert. It 

 would therefore seem probable that comparatively few species 

 would employ this route and indeed not a single species is known 

 certainly to migrate from Arizona or Utah to the Mackenzie Valley, 

 and from a study of the data it seems that hardly half a dozen 

 species can possibly travel this route. 



There is a modification of this route which ought apparently to 

 form a convenient and fairly direct course from Mexico or Texas 

 to the Mackenzie Valley. This is along the foothills of the Rocky 



