CHAPTER IV 



Annual Migrations 



We can now pay some attention to the possible 

 stimuli that call forth the migratory impulse twice 

 annually with special reference to conditions as we 

 see them in the North. In other parts of the globe 

 where migrations occur the effective stimuli need 

 not necessarily be the same. It is, indeed, more 

 than likely that they will differ but the general 

 principle will be similar. 



All told there are about 30 species of birds that 

 winter in the Edmonton district and to the north, 

 out of a total list of some 300 — approximately 10 

 per cent ; or to put it another way, nearly 90 per cent 

 of the birds occurring in Alberta and northwards 

 are migratory. This includes Alberta passage 

 migrants, species breeding in the Arctic. Although 

 the southward passage is not as precisely according 

 to schedule as the northern it is, nevertheless, 

 strikingly accurate with many species. That it 

 should be more protracted and spread out is to be 

 expected for young, which with many species travel 

 later than their parents, are involved and in other 

 cases the adults themselves may be seriously held 



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