1920] Sivarth: Revision of Avian Genus Passerella 105 



given direction, but that appreciable changes in appearance do not 

 occur wherever there is discontinuity of range. 



Passerella is closely related to Melospiza. Fox sparrows are very 

 like song sparrows, in structure, appearance, habits, and actions. The 

 respective ranges also of Passerella iliaca and Melospiza melodia are 

 suggestive of rather close relationship between the two, for their 

 habitats are in a measure complementary since the two species, though 

 frequently occurring in the same general regions, occupy different life 

 zones. Passerella is mostly in the Boreal zone, descending occasion- 

 ally into high Transition, Melospiza mostly in the Sonoran zones, 

 though some races ascend to Transition and higher. On the coast 

 of Alaska, at the northern extreme of the range of Melospiza, the 

 general separation of the two does not hold, neither Sonoran nor 

 Transition extending this far north, but at the latitude of Vancouver 

 Island we find the birds thus separated, Passerella on the Boreal 

 mountain tops, and Melospiza in the Transition zone valleys. 



All of the races of Passerella ilia&a are migratory. Some are much 

 more so than others, and in a general way it may be said that the 

 subspecies breeding farthest north migrate farthest south. 



Passerella iliaea iliaca winters far south of its Boreal nesting 

 grounds, concentrating into a relatively limited area in the South 

 Atlantic and Gulf states. Thus the lines of migration in this sub- 

 species converge, birds from Labrador and Newfoundland traveling 

 southwest and those from Alaska and Mackenzie southeast, toward 

 their common winter home. 



Birds of the Unalaschcensis group move directly southward along 

 the Pacific coast, each into a more or less definitely circumscribed 

 winter habitat. The six subspecies of this group are arranged in 

 summer, from north to south (from the Alaska Peninsula to Puget 

 Sound) in the following order: unalaschcensis, insularis, sinuosa, 

 annectens, townscndi, fuliginosa. The subspecies breeding at the 

 northern extreme, unalaschcensis, insularis and sinuosa, move the 

 farthest south in winter, passing completely over both summer and 

 winter habitats of annectens, townsendi and fidiginosa, and reaching 

 the extreme southern limits of California. Annectens winters mainly 

 on the coast of California in the Santa Cniz and San Francisco Bay 

 regions, passing over the habitats of townsendi and fidiginosa to reach 

 this destination. Townsendi in turn leap-frogs over fidiginosa and 

 winters in numbers as far south as Humboldt Bay, California. 

 Fuliginosa hardly migrates at all. Occasional stragglers reach San 



