6 



The Chestnut-sided Warbler, Rose-breasted Grosbeak, Least Fly- 

 catcher, Wilson's Thrush and Savanna Sparrow are also found 

 bi-eeding in the Alleghanian Zone, none of which occur, except as 

 migrants, in the Carolinian Belt. The Scarlet Tanager, Black and 

 White Warbler and Redstart are also characteristic species of the 

 Alleghanian Zone, and, though they breed also in the Carolinian, are 

 less abundant there. 



The Canadian Zone occupies in Pennsylvania only the tops of the 

 highest mountains and the elevated plateau region, where the deep 

 hemlock forests, with their cold brooks and dense shade, still remain 

 undisturbed. The passage from the Alleghanian to the Canadian 

 Zone is here, as a rule, remarkably distinct, as the more northern 

 birds keep strictly to the virgin forest, the cool shade of which affords 

 them a congenial summer home. Where the forest has been re- 

 moved the Canadian species for the most part disappear, and, judg- 

 ing from present indications, it would seem that this element in our 

 fauna, which once undoubtedly extended over a much greater area 

 than at present, may soon almost entirely disappear, as the lumber- 

 men year by year encroach upon the forest tracts. 



The Canadian Zone, as exhibited in the Alleghanies, consists of a 

 series of isolated patches or "islands," which are quite separated 

 from the main portion of the zone in the north, the elevation above 

 the sea level in the isolated portions producing climatic conditions 

 similar to those experienced in the lowlands at more northern lati- 

 tudes. In addition to the mountain tops of Pennsylvania, Virginia 

 and North Carolina, the Canadian Zone includes the Catskills and 

 Adirondacks, while the main portion of the zone stretches from the 

 White Mountains and Maine north to southern Labrador and New- 

 foundland, and northwest to southern Alaska. Between the Cana- 

 dian and the Arctic lies the Hudsonian Zone. 



Birds which characterize the Canadian Zone in the breeding season 

 are the Canadian, Black-throated Blue, Blackburnian and Magnolia 

 Warblers, the Winter Wren, Brown Creeper, Hermit and Olive- 

 backed Thrushes. Many other species breed regularly in the more 

 northern portion of the zone, such as the White-throated Sparrow, 

 Three-toed Woodpecker, Tree Sparrow, Fox SpaiTow, etc., but none 

 of these have yet been found breeding either in the Pennsylvania 

 mountains or farther south. 



