MIGRATION AND ORIGINS 



267 



tory habits are established among these maritime species which nest 

 in Alaska and Yukon. In none of these maritime species, however, 

 have the specialized migratory habits resulted in the visible differ- 

 entiation which distinguishes the resident and most of the migratory 

 populations of land birds which are restricted in nesting to Alaska 

 and Yukon. Judging from their powers of flight and adaptability 

 to arctic conditions these species could have been among the earliest 

 to come to Alaska after the last glacial maximum. It appears that 

 the isolation produced by special migratory paths and special nesting 

 areas is broken down by behavior after nesting which leads to mixing 

 with the remainder of the species. Here the specific behavior has 

 prevented physical differentiation. 



Table 10. — Birds wintering or migrating along American Pacific coasts 

 [Explanation— (P) present.] 



Birds 



Anak- 

 tuvuk 



Kobuk 



Old Crow 



Range ef 

 the species 



Gavia immer 



P 



P 



P 



Am 



Qavia adamsi 



P 



P 





Eu As Am 



Gavia arctica paciflea 



P 



P 



P 



Eu As Am 



Gavia stellata 



P 



P 



P 



Eu As Am 



Podiceps grisegena holbollii 





P 



P 



Eu As Am 



Podiceps auritus cornutus 



P 



P 



P 



Eu As Am 



Olor columbianus 



P 



P 



P 



Am 



Branta nigricans 



P 



P 



P 



Am 



Chen hyperborea hyperborea 



P 



P 



P 



Am 



Aythya marila nearctica 



P 



P 



P 



Eu As Am 



Bucephala clangula americana 







P 



Eu As Am 



Bucephala islandica 







P 



Am 



Bucephala albeola 





P 





Am 



Histrionicus histrionicus 



P 



P 



P 



Am 



Clangula hyemalis 



P 



P 



P 



Eu As Am 



Melanitta deglandi 



P 



P 



P 



Am 



Melanitta perspicillata 



P 



P 



P 



Am 



Oidemia nigra americana 





P 





Eu As Am 



Mergus serrator serrator 



P 



P 



P 



Eu As Am 



Aquila chrysaetos canadensis 



P 



P 



P 



Eu As Am 



Haliaeetus leucocephahis alascanus 



P 



P 



P 



Am 



Squatarola squatarola 



P 



P 





Eu As Am 



Numenius phaeopus hudsonicus 



P 



P 



P 



Eu As Am 



Eroha alpina paeifica 



P 



P 





Eu As Am 



Crocethia alba 



P 



P 





Eu As Am 



Phalaropus fulicarius 



P 



P 





Eu As Am 



Lobipes lobatus 



P 



P 



P 



Eu As Am 



Stercorarius pomarinus 



P 



P 





Eu As Am 



Stercorarius parasiticus 



P 



P 



P 



Eu As Am 



Stercorarius longicaudus 



P 



P 



P 



Eu As Am 



Larus hyperboreus barrovianus 



P 



P 



P 



Eu As Am 



Larus canus brachyrhynchus 



P 



P 



P 



Eu As Am 



Lams Philadelphia 





P 



P 



Am 



Xema sabini 



P 



P 





Eu As Am 



Sterna paradisaea 



P 



P 



P 



Eu As Am 



Total (.36) 



(30) 



(34) 



(26) 





