ENVIRONMENT, PAST AND PRESENT 53 



Canada-United States boundary. The extreme tip 

 of Patagonia would fall short of Edmonton, while 

 Africa would have to be lengthened by nearly 200 

 miles to reach the latitude of Washington, D. C. 

 A majority of the birds of the northern hemisphere 

 thus come to summer and breed in localities much 

 further removed from the equator than birds of 

 the southern, while dozens of species breed more 

 than double the distance from the equator than do 

 even the southernmost breeders of Australia. They 

 come under the influence of conditions, to be con- 

 sidered in detail below, that are entirely unknown 

 to all but a few birds of the southern hemisphere, 

 an extremely important fact but seldom appreciated. 



We propose then, to pay particular attention to 

 the well-known migrations of the northern hemi- 

 sphere. Nowhere else can migrations be more favor- 

 ably observed or more critically studied. If we 

 can analyse them here we can apply our findings to 

 migrations elsewhere after making due allowance for 

 other factors. 



In order to have something specific in our minds, 

 let us review meteorological figures for the Edmonton 

 district. In general one may say that the further 

 north the more severe are the winter conditions, 

 though it must be remembered that exceptional 

 areas, such as the coast of Alaska, exist. But what- 



