2o8 THE MIGRATIONS OF BIRDS 



entirely in South America, from Ecuador and Gui- 

 ana to eastern Brazil. The migration flight is per- 

 formed through the West Indies, so that birds from 

 the northwest and northeast converge toward Cuba 

 in southward flight. Both spring and autumn move- 

 ments are comparatively late, and in spring, when 

 the lazy song of the black-poll is heard, we know 

 that the close of migration is near at hand. The 

 rate at which the bird travels is rapid, so that for 

 its entire course through the United States it ad- 

 vances at the average rate of about seventy-five 

 miles per day. Professor Cooke estimates that the 

 final spring flight through northwestern Canada 

 proceeds at an average rate of two hundred miles 

 per day. 



Much of the migration of wood warblers is per- 

 formed by night, but in spring or autumn we often 

 find mixed flocks feeding along through tree growth 

 in the general direction in which migration is pro- 

 ceeding. At times, late in the autumn, this move- 

 ment is especially noticeable, and often warblers 

 come flying in from the north, to work hurriedly 

 through the trees for a few moments and then, with 

 soft calls, rise and pass on out of sight to the south. 

 Feeding flocks move rapidly in the same direction, 

 so that the distance covered in the course of early 

 morning and late afternoon, when the birds are 

 particularly active, must be considerable. Flights 



