MIGRATION AND ORIGINS 275 



to migrate across 100 degrees of longitude to reach Yukon. This is a 

 remarkable flight for a bird weighing 24 grams. And from its nearest 

 known wintering place in the Philippines (Parkes and Amadon, 1948) 

 Kennicott's willow warbler {Phyllosco'pus) also travels eastward about 

 100 degrees of longitude to nest in central arctic Alaska. It weighs 

 less than 10 grams. 



The two species which fly over the Pacific (table lie) also fly along 

 its shores. Present records give no clue as to their Alaskan landfall. 



Along the arctic coast of Alaska a powerful trend of bird migra- 

 tion moves eastward in spring, in contrast to the predominant west- 

 ward trend of land birds in the Yukon Valley. These eastbound 

 migrants along the arctic coast may be assigned to three groups, 

 according to the length of their arctic flight courses. One includes 

 the birds wintering on north Pacific coasts (table 10). At Barrow 

 flights of brant, some shore birds, gulls, and terns are often seen 

 migrating eastward in spring and westward at the end of siunmer. 

 On the eastern arctic coast of Alaska, Dixon (1943) remarked east- 

 bound flights of loons, brant, and other geese in June and westbound 

 flights of brant in August. It has been my impression that along 

 the coast near Barrow the flights of these North Pacific wintering 

 birds break up in spring and assemble in late summer. East of 

 Barrow the flights of these birds appear to diminish, while west- 

 ward they are more often reported, so that coastwise migration of 

 North Pacific wintering birds tapers off between Barrow and eastern 

 Alaska. 



At Barrow some of the migrating loons, geese, ducks, and sand- 

 pipers appear in spring as if they were arriving from the interior. 

 Before we began our studies at Anaktuvuk, Thomas Brower believed 

 there were indications on the coast that many water birds, and prob- 

 ably all land birds, coming to the arctic slope and coast had passed 

 through the Brooks Eange. My occasional observations in the coun- 

 try between the coast and mountains showed that many birds were 

 coming from the south in spring and forming flocks for southward 

 migration in late summer. At Anaktuvuk, in the Killik Valley, and at 

 Howard Pass the migratory movements I have seen were sufficient 

 to bring large numbers of birds to the arctic slope and coast. 



A second group of species, which migrates northward over 

 Bering Sea and then east along the arctic Alaskan coast, contains 

 members of the great bird associations characteristic of the Bering 

 Sea coast in summer. The distinctive birds are cormorants, auks, 

 murres, guillemots, and puffins. These species reach Barrow and 

 individuals occasionally pass eastward, but their abundance rapidly 

 diminishes east of Cape Lisburne, where the last good nesting cliffs 

 are found. 



