106 University of California Piiblications in Zoology [Vol. 21 



Francisco Bay aiid a few more winter in the Humboldt Bay region, 

 but the main winter home of tliis subspecies certainly lies north of 

 the latter point. Undoubtedly, however, it performs an altitudinal 

 migration, moving down from the mountain tops which constitute its 

 summer home, as on Vancouver Island. (See fig. H.) 



Fig. H. Map showing in somewhat conventionalized form the nature of the 

 migrations performed by the subspecies of the Unalascheensis group. 1, unaJasch- 

 censis; 2, insularis; 3, sinuosa; 4, atmectens; 5, towmendi; 6, fuliginosa. A solid 

 line surrounds the summer habitat; a dotted line surrounds the main winter habitat. 

 The broken lines connecting summer and winter habitats do not necessarily ind.i- 

 cate migration routes; they are inserted to emphasize the overleaping feature in 

 the seasonal movements. The subspecies occupying the northernmost summer 

 habitats {unalasolierms, insularis, and sinuosa) travel the farthest south. The 

 subspecies occupying the southernmost summer habitat {fuliginosa) is practically 

 resident there. 



As bearing upon the manner in which these birds migrate, certain 

 facts gathered during several seasons of field work carried on by the 

 California Museum of Vertebrate Zoology on the coast of Alaska and 



