9 



Lands End in England, illustrates the enormous effect of the cold Arctic 

 current, coming down from Davis strait, in contrast with the influence of 

 the warm Gulf stream that dies against the English shores. 



We can also observe minor groupings that are based upon conditions 

 other than temperature, these determining factors being mostly variations 

 of humidity. Thus the life of the eastern woodlands is plainly different 

 from that of the more arid plains of the prairie provinces and both are 

 strikingly different from that of the moist Pacific slope. 



Taking the eastern forms as typical in the ordinary acceptance of the 

 word, comparable birds of the prairie are slightly smaller and considerably 

 paler in coloration, whereas on the humid Pacific coast they are larger 

 and much darker in colour. Through these influences, therefore, we find 

 in the west many subspecies of eastern forms. Comparatively few species 

 range unmodified across the continent, many are represented east and west 

 by two or more subspecies showing greater or less differentiation, and in 

 other cases they are replaced by closely allied species or are absent 

 altogether. 



In noting these faunal divisions, however, it must be remembered 

 that as far as birds are concerned, these associations have to be based 

 entirely upon breeding individuals. Birds travel so widely and along so 

 many devious routes in their migration, that they may pass through several 

 faunal areas in spring and autumn though breeding in only one. Therefore, 

 in determining the faunal zone to which any given area should be referred, 

 such transients must be disregarded. 



Though the distributions given under the following specific headings 

 are rather vague, many tend to follow similar general lines. Thus some 

 are given as "the lower Great Lakes region"; these are probably Upper 

 Austral forms. "Southern Ontario and Quebec" refers to Transition 

 species, whereas "beyond dense settlement or to the limit of cultivation" 

 refers, naturally, to species of the Canadian zone. 



The following species are given as representative of what birds are to 

 be expected in each zone: 



Upper Austral 'Canadian Arctic 



Cardinal Hudsonian Chickadee Ptarmigan 



Orchard Oriole Red-breasted Nuthatch Snowy Owl 



Carolina Wren Olive-backed Thrush Snow Bunting 



Grasshopper Sparrow Three-toed Woodpecker Gyrfalcon 



Blue-grey Gnatcatcher Hermit Thrush. Longspur 



Dickcissel White-throated Sparrow 

 Canada Jay 



Transition 1 Grey-cheeked Thrush 



Bobolink Slate-coloured Junco 

 Wood Thrush 



Yellow-throated Vireo Hudsonian 



Baltimore Oriole Rough-legged Hawk 



Towhee Fox Sparrow 



Cuckoo Northern Shrike 



Field Sparrow White-crowned Sparrow 



Bluebird Pine Grosbeak 



Catbird American Pipit 



i Most of the species of this zone also occur in the Upper Austral, but reach their northern limit here. The occur- 

 rence of these with the absence of the species of bordering zones are the most marked characteristics of the TL ransi- 

 tion zone. 



