STATUS AND DISTRIBUTION 255 



infrequently apparent. What it shows is that some birds are curious, 

 restless, or otherwise unconstrained by the influences which hold the 

 rest of their populations to their present nesting grounds. A very 

 elaborate and unlikely conjunction of physiological and environmental 

 conditions would be necessary to expand or contract a well established 

 nesting area. The persistence of visiting nevertheless suggests that 

 inherent inclinations exist which could, under special conditions, ef- 

 fectuate an increase in range. The long persistence of the occasional 

 expression of the tendency shows how seldom it changes the range of a 

 population and indicates the essential conservatism of bird distribu- 

 tion at Anaktuvuk. 



The Birds of Kobuk 



At first view the Kobuk avifauna as summarized in table 4, seems not 

 to differ as much from that of Anaktuvuk as do the environmental con- 

 ditions. Kobuk is in a wooded valley, Anaktuvuk is in mountain 

 tundra. Climatically they differ, in that at Kobuk frost-hardy vege- 

 tables can be grown in the usual summer warmth, whereas at Anak- 

 tuvuk warm summer days are too infrequent for growing vegetables 

 and hard freezes occur there as often as mild summer frosts at Kobuk. 



A rather large difference appears in the status of the birds of the 

 two areas, for whereas at Anaktuvuk 22 are summer visitors from their 

 nearby ranges, at Kobuk only 10 species, because they are not known 

 to nest or normally migrate there, are considered to be summer visitors. 

 The winter best demonstrates the large difference between biotic con- 

 ditions on the tundra and in the forest, for only 7 birds are regular 

 winter residents at Anaktuvuk in contrast with 23 at Kobuk. 



Numerous other differences are apparent to the observer who has 

 lived in these places. Swallows are rare visitors to Anaktuvuk whereas 

 three species nest at Kobuk. Six species of warblers nest in large 

 numbers at Kobuk, but only one has been occasionally found nesting 

 at Anaktuvuk. Several species of sandpipers, common along the 

 tundra streams, are scarce in the wooded valleys, and at Kobuk long- 

 spurs (Calcarius), pipits (Anthinus), and larks {Eremophila) are to 

 be found only in the tundralike elevations above the valley floor. 



Large migratory flights of geese and ducks and lesser flights of gulls 

 pass along the Kobuk River in spring, the gulls appearing to come 

 from the coast. It is not apparent whether the geese and ducks come 

 from the interior or from the coast, but flights of geese can be often 

 seen to leave the river for the north. The direction of migration of 

 small birds is especially obscure in wooded country. Since most of 

 the land birds and many of the shore birds migrate northward through 

 western Canada, these must have traveled some 500 miles westward 

 across Alaska in order to reach Kobuk. The few records of arrivals 



