450 Cooke, Bird Migration in the Mackenzie Valley. [bet. 



But the fact that the Mississippi Valley birds pass to the Macken- 

 zie Valley cannot be proved by dates of migration as is shown by 

 the following records. The Canada Goose begins its migration near 

 the Mississippi river in February. About the twentieth of that 

 month may be considered the date of its normal arrival in south- 

 eastern Iowa. Passing slowly north it appears one month later in 

 southeastern Minnesota at the end of the first week in April. Mi- 

 gration in southeastern Nebraska commences at about the same 

 time as in southeastern Iowa, but the birds move north a trifle 

 faster and cross to Saskatchewan about the first of April. Further 

 west the Canada Goose winters not far south of the United States 

 boundary and crosses into southern Alberta the last of March. On 

 the Pacific coast the species winters in British Columbia. When, 

 therefore, it is known that the Canada Goose arrives at Lake Atha- 

 baska April 20, no certain conclusion can be drawn from this data 

 as t© whether these earliest birds come from Manitoba, Alberta, or 

 British Columbia. The last furnishes its most northern winter 

 home and hence would require the least rapid migration in spring 

 to reach Lake Athabaska by the given date. The journey by way 

 of Manitoba or eastern Saskatchewan is a longer distance and the 

 later start requires a higher speed of migration. Hence if no other 

 information was available, the migration dates alone would lead 

 one to suppose that the earliest birds at Lake Athabaska came from 

 the southwest. But as stated at the outset, the relative numbers 

 of the birds east and west of the Rocky Mountains, make it certain 

 that most the birds of Lake Athabaska really do come from the 

 Mississippi Valley. Since this is true of the geese, it may be 

 assumed to be true also of the Mallard and Pintail Ducks which 

 travel in company with the geese and have the same range from 

 the Atlantic to the Pacific. 



The same method of reasoning may be applied to the larger part 

 of the fifty-eight species of wide-ranging waterfowl that occur regu- 

 larly at Lake Athabaska. Most of them are abundant in migration 

 across the moist plains from Kansas to Saskatchewan, but are com- 

 paratively rare in the whole mountainous region of western United 

 States where favorable localities either for breeding or for feeding 

 during migration are few and of small area. Hence it must be true 

 in general that the untold thousands of water birds that frequent 



