large numbers in the Mississippi Valley, including eastern South 

 Dakota, and in southeastern Manitoba, there are few records anywhere 

 along the route of such great flocks as are known to winter in Louisiana. 

 When the birds arrive in the James Bay region of Canada they appar- 

 ently enjoy a prolonged period of rest, as they are not noted in the 

 vicinity of their breeding grounds until the first of June. During the 

 first 2 weeks of that month they pour into the tundra country by the 

 thousands, and each pair immediately sets about the business of rearing 

 a brood. 



The robin has been mentioned as a slow migrant, and as a species it 

 takes 78 days to make the 3,000-mile trip from Iowa to Alaska, a stretch 

 of country that is crossed by advancing spring in 68 days. In this case, 

 however, it does not mean that individual robins are necessarily slow, 

 for probably the northward movement of the species depends upon the 

 continual advance of birds from the rear, the first individuals arriving 

 in a suitable locality remaining to nest, while the northward movement 

 of the species is continued by those still to come. 



Special interest attaches to the great variation in the speed at which 

 birds travel in different sections of the broad flyway extending from 

 the Gulf of Mexico to the Arctic Ocean, by way of the Mississippi and 

 Mackenzie Valleys. The blackpolled warbler furnishes an excellent 

 example (fig. 6). This species winters in north-central South America 

 and migrates in April across the West Indies to Florida. From this 

 point some individuals fly northwest to the Mississippi Valley, north to 

 Manitoba, northwest to the Mackenzie River, and thence almost due 

 west to western Alaska. In tracing the long route of these birds it is 

 found that a fairly uniform average speed of 30 to 35 miles a day is 

 maintained from the Gulf to Minnesota. Then comes a spurt, for a 

 week later the blackpolls have reached the central part of the Mac- 

 kenzie Valley and by the following week they are observed in north- 

 western Alaska. During the latter part of the journey, therefore, many 

 individuals must average more than 200 miles a day. They use 30 

 days in traveling from Florida to southern Minnesota, a distance of 

 about 1,000 miles, and scarcely half that time to cover the remaining 

 2,500 miles to Alaska. It should be noted that the increased speed is 

 directly associated with the change in direction, the north-and-south 

 course in the Mississippi Valley being accomplished slowly while the 

 northwesterly course across Canada is made at a much greater speed. 

 Increased speed across western Canada to Alaska is also shown by many 



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