no THE MIGRATIONS OF BIRDS 



mountains of the southwest are better understood. 

 In July and August, when flowers bloom in abun- 

 dance in mountain parks at altitudes of 7cxx) to 9000 

 feet in the Chiricahua, Huachuca, and near-by 

 mountain ranges, hummingbirds of several species 

 fairly swarm. Many do not breed here but come 

 from near-by, though as yet the exact status of such 

 species as the white-eared hummer is uncertain. 



Rapidity of Migration Movement 



The rapidity with which migration progresses 

 when birds are passing to the north in spring seems 

 to depend to a considerable extent, among small 

 species at least, upon whether migration begins 

 early or late in the season. Professor W. W. Cooke, 

 in his studies on bird migration, gathered and pub- 

 lished numerous data on this point from records 

 furnished by a large corps of observers scattered 

 through the country, who made careful record of 

 dates of first arrival in their vicinity. Professor 

 Cooke found that the average rate for the month of 

 March, when early migrants were retarded by fre- 

 quent periods of bad weather, was considerably less 

 than that for April, while in May all migrants 

 seemed to travel at a much more rapid pace. From 

 this it is deduced as a general rule that those species 

 that start their migration late in spring travel to 

 their breeding grounds at a much more rapid rate 



