MIGRATION AND ORIGINS 



277 



Figure 8. — Main migration routes in northwestern America. Large circles (1-3) mark lo- 

 calities where comprehensive observations have been made by the author. Numbers 4-10 

 mark localities where observations have been made several times for brief periods, or 

 once over a period of at least 3 weeks. 



Explanation: 



1 — Anaktuvuk 

 2— Kobuk 

 3— Old Crow 

 4 — Barrow 



5 — Ahlasuruk River 

 6— Killik River 

 7 — Chandler Lake 



8 — Alatna River 

 9— Bettles 

 10— Big Lake 



(table 9) . Thus, 23 local populations are distinguished taxonomically 

 out of 28 resident and migratory species which nest mauily in northern 

 Alaska and Yukon. 



The migratory species come from wintering grounds in America and 

 Asia distributed over at least 170 degrees of longitude, or nearly half 

 of the circumference of the earth. The diversity of their winter ex- 

 perience stands in contrast to the similarity of their summer experi- 

 ence on the breeding ground which they occupy for only about three 

 months of the year. If we assume that the races nesting in northern 

 Alaska and Yukon became differentiated as a result of their segrega- 

 tion there as isolated breeding populations, the formation of 23 dis- 

 tinguishable races out of 28 species is a significant step in the separa- 

 tion of species into races. The characters by which the local races are 

 distinguished are matters of color, pattern, or dimensions to which 

 no adaptive value can be assigned and so, as far as can be seen, it is 



