458 Cooke, Bird Migration in the Mackenzie Valley. [oct! 



The migration route of Calcarius pictus is evident since the great 

 majority of the individuals are confined during migration and winter 

 to a narrow belt of plains country extending from Texas northward 

 to the Saskatchewan and thence northwestward along the Macken- 

 zie to the summer home on the Barren Grounds of the Arctic. The 

 same route is followed more or less closely by Passerherbulus 

 lecontei, Spizella pallida, and Calcarius lapponicus alascensis. 



One of the strangest migration routes to the Mackenzie Valley is 

 that of the Yellow-bellied Sapsucker (Sphyrapicus v. varius). The 

 mouth of the Nahanni River a hundred miles northwest of Fort 

 Simpson forms the normal limit of the species' range in that direc- 

 tion; this is in longitude 124° W. The Yellow-bellied Sapsuckers 

 breeding here come by way of Minnesota at least as far east as 

 longitude 96° W. The range of this species extends thence south 

 through western Missouri on the meridian of 94° and then south- 

 west through the whole eastern half of Texas to at least longitude 

 103° W. in southwestern Mexico. Thus the migration route forms 

 a bow, the southern half extending through nine degrees of longitude 

 in a portion of the globe where this is equal to six hundred miles, 

 and the northern half through thirty degrees of longitude, equi- 

 valent in those high latitudes to nine hundred miles. 



The above routes account for the different groups of species 

 breeding in the Mackenzie Valley as follows: 



Eastern species ranging in the central United States only 

 to the edge of the Plains. 33 



Eastern species ranging regularly or occasionally to the 

 Rocky Mountains in the central United States. 19 



Species that in migration or during the winter occur across 

 the whole United States from the Atlantic to the Pacific. 82 



Western species confined almost entirely to the Pacific 

 coast. 9 



Western species, ranging only occasionally east of the 

 Rocky Mountains in the central United States. 3 



Western species, ranging to the eastern edge of the Plains 

 in the central United States. 15 



Total migratory species breeding in the Mackenzie Valley, 

 and wintering to the southward. 161 



In addition to these, the list of the birds of the Mackenzie 



