8 U. S. NATIONAL MUSEUM BULLETIN 217 



of a faunal group which would well indicate the relations between 

 the animals and their environment. There are a sufficient number 

 and variety of birds, and their taxonomic relations are well worked 

 out. Like ourselves, birds are principally directed by sight and sound 

 in activities by daylight, and so they demonstrate themselves to our 

 senses as to their own. Consideration of the relations of animals to a 

 country brings to mind their connection with populations of other 

 regions, and the visible flight of birds indicates how populations are 

 distributed. In particular the migrations of birds had impressed upon 

 my interest that their courses annually exhibit the operation of distri- 

 butional inclinations which are invisible in sedentary animals. 



I did not anticipate in 1947 that for the ensuing 12 years I would 

 be studying adaptations to life in arctic Alaska, nor did I then realize 

 how many biologists would become associated in their attention to 

 that area. But after several years it was apparent that the bird life of 

 arctic Alaska indicated it to be a well characterized faunal region, 

 and I was led to look for the geographic features by which the environ- 

 ment might be defined as a habitat for its somewhat special fauna. 



Physiography of Arctic Alaska 



The principal physiographic feature of arctic Alaska (fig. 1) is the 

 Brooks Eange, which extends eastward near the 68th parallel from 

 Cape Lisburne for about 700 miles to the Mackenzie Delta. In east- 

 em Alaska the peaks of the Brooks Eange rise above 9,000 feet. 

 They diminish in the center to about 7,000 feet, and to about 4,000 

 feet within 100 miles of the western coast. In the northern watershed 

 are many short swift rivers, the central ones draining into the Colville, 

 which flows eastward through the rolling tundra of the arctic slope. 

 East of the Colville mouth the coast approaches close to the moun- 

 tains, and north of the Colville the arctic slope gradually lowers to 

 a flat coastal country of many lakes. 



Along the southern watershed the westerly flowing Koyukuk Kiver 

 receives the rivers from the central mountains of the Brooks Eange 

 while those in the east drain into the Yukon and Porcupine. The 

 Noatak Eiver runs west from the western Brooks Eange and enters 

 Kotzebue Sound just north of the Kobuk Eiver ; together they drain 

 the southwestern base of the Eange. Although the Kobuk is not con- 

 nected with the Yukon Eiver, its southern watershed is open at low 

 elevations to the Koyukuk Valley and so to the Yukon Valley. The 

 Koyukuk Eiver flows into the Yukon and from its upper valley a 

 broad low pass leads to the upper Yukon Valley. In Yukon Terri- 

 tory the Porcupine Eiver, draining the southeastern watershed of the 

 Brooks Eange, forms a continuation of the Yukon Valley. The south- 

 em watershed of arctic Alaska thus is the northern part of the great 



