10 



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

 be expected in each zone: 



Upper Aiistral Canadian Arctic 



Cardinal Hudsonian Chickadee Ptarmigan 



Orchard Oriole Red-breasted Nuthatch Snowy Owl 



Carolina Wren OUve-backed Thrush Snow Bunting 



Grasshopper Sparrow Three-toed Woodpecker Gyrfalcon 



Blue-grey Gnatcatcher Hermit Thrush Longspur 

 Dickcissel 



Transition^ 

 Bobolink 

 Wood Thrush 

 Yellow-throated Vireo 

 Baltimore Oriole 

 Towhee 

 Cuckoo 

 Field Sparrow 



Bluebird 

 Catbird 



Hudsonian Chickadee 

 Red-breasted Nuthatch 

 Olive-backed Thrush 

 Three-toed Woodpecker 

 Hermit Thrush 

 White-throated Sparrow 

 Canada Jay 

 Grey-cheeked Thrush 

 Slate-coloured Junco 



Hudsonian 



Rough-legged Hawk 

 Fox Sparrow 

 Northern Shrike 

 White-crowned Sparrow 

 Pine Grosbeak 

 American Pipit 



MIGRATION. 



The migration of birds, their periodical and seasonal appearance and 

 disappearance, is one of the most obvious phenomena of nature. The 

 fact that many birds disappear in winter is common knowledge and has 

 attracted attention for ages. Though once regarded as a mystery, and still 

 far from being throughly understood in many of its details, we are beginning 

 to wonder less but admire more as accurate knowledge gives place to vague 

 speculation. To-day, where most of our northern species spend the winter 

 is known and many of the routes by which they come and go have been 

 mapped out. We know that on the whole they are governed by ordinary 

 and well known, though perhaps highly developed, senses and common 

 every day influences, and not by the mysterious powers and instincts once 

 ascribed to them. 



The fundamental cause of migration is obviously the waxing and the 

 waning of the food supply. Birds leave the northern land of their birth 

 because there is no other way by which to avoid starvation. Many species 

 can withstand extreme cold but none can go long without food and though 

 some bird food still remains in Canada throughout the winter, its amount 

 is small and only sufficient for a limited population and even that supply 

 rapidly decreases, or to the north is buried under deep snow. The cause 

 of the SOU'"" yard migration in the autumn then is obvious, but why should 

 a bird leave the soft climate and plentiful food supply in the south to brave 

 dangerous travel and finally find itseK in a land where retiring winter still 

 lingers and the danger of starvation is imminent. Many ingenious explan- 

 ations have been advanced to account for this, longing or homesickness 

 for the land of birth, hereditary memories of an ancient home enduring 

 through geological ages, the seeking of special food for nestlings, and 

 insufficiency of nesting sites in the southern areas, have all been given as 

 possible reasons. However, it is unnecessary to advance a complicated or 

 far-fetched explanation when a simple and direct one exists. If we 

 remember that in the nesting season the bird population is increased many 



iMost of the species of this lone also occur in the Upper Austral, but reach their northern limit here. The occur- 

 rence of these with the absence of the specieB of bordering zonee are the most marked characteristics of the Transition 

 zone. 



