10 
INTRODUCTION 
Canadian — 
Brown-headed Chickadee 
Olive-backed Thrush 
Hermit Thrush 
Three-toed Woodpeckers 
Canada Jay 
White-throated Sparrow 
Junco 
H udsonian — 
Fox Sparrow 
Northern Shrike 
White-crowned Sparrow 
Bohemian Waxwing 
Evening Grosbeak 
Pine Grosbeak 
Arctic — 
Leucosticte 
Eider Ducks 
Snow Bunting 
Gyrfalcon 
Lapland Longspur 
Ptarmigan 
Snowy Owl 
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 thoroughly understood in many of its details, we are beginning 
to wonder less but admire more as accurate knowledge replaces vague 
speculation. Today we know where most of our northern species spend 
the winter and many of the routes by which they come and go have been 
mapped. 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 remains in Canada throughout the winter, its amount is 
sufficient for only a limited population and even that supply rapidly 
decreases, or, to the north, is buried under deep snow. The cause of the 
southward 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 to a land where retiring winter still lingers and the danger 
of starvation is imminent? Many ingenious explanations have been 
advanced to account for this: homesickness, hereditary memories of an 
ancient home that have endured 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 an extraordinary explanation, when a simple one exists. If 
we remember that in the nesting season the bird population is increased 
many times by the birth of young; that though in winter there may be 
room for a considerable number of birds in the southern stations, the 
natural spring increase in population outgrows the supporting power of 
even that fruitful land; and that just at this critical time the whole northern 
temperate region is by the coming of summer thrown open to occupation 
with an abundance of food, the subject is less mysterious. In fact, only by 
migration is it possible to use the supporting power of the temperate regions 
unless the birds fast or hibernate through the winters, to neither of which 
customs the avian nature takes kindly. Though food supply was the 
fundamental or originating reason for migration we must look for other 
and more immediate impulses for an explanation of its methods today. 
Originally forced to and fro by hunger, the annual movements now have 
become instinctive and take place before the actual hunger pinch is felt, 
or the physical system is weakened by want. It is much as with ourselves. 
We eat to prevent starvation, but habit calls most of us to the table at 
