cies travel northward at the rate of forty miles a 

 day, and still farther north some at seventy-two 

 miles, others at one hundred and sixteen miles, and 

 five species, on arriving in Alaska, are traveling at 

 the rate of one hundred and fifty miles a day. 



The figures here given are for the species as a 

 whole, not for individual birds. Usually birds mi- 

 grate only a few hours during the night and then 

 rest for a day or two, so that the average rate at 

 which a species migrates is much less than for an 

 individual bird. Our common small birds prob- 

 ably travel at the rate of about thirty miles an hour 

 while migrating; ducks and geese may travel at the 

 rate of forty-five miles an hour. Thus during a 

 single night birds may travel from two hundred to 

 four hundred miles. 



Daily time of migration. Some birds migrate by 

 day, some by night, and some both by day and 

 night, but most are night travelers. The time se- 

 lected by a bird for migration depends on its power 

 of flight, its method of procuring food, and its dis- 

 position. The warblers, vireos, and thrushes mi- 

 grate by night, the swallows and hawks by day; 

 while ducks, shore-birds, and sea-birds migrate both 

 by day and night. 



Routes. As birds travel between their winter and 

 summer homes, it is found that they follow fairly 

 well-defined routes. In the central United States 

 the ^Mississippi Valley is the most common route, 



