OUR GREATEST TRAVELERS 



363 



ent in color and in pattern of coloration. 

 Birds of the western style are not known 

 north of southwestern Saskatchewan, 

 central British Columbia, and southeast- 

 ern Alaska, while the whole country to 

 the northward is occupied by birds that 

 evidently have come from the southeast. 

 The heavy, solid line on the map shows 

 the approximate meeting-ground of the 

 two forms. 



Most migrants except the robins, 

 ducks, and geese wait in their warm 

 winter quarters until springtime is far 



advanced, and then, traveling swiftly, 

 occupy only a few days in their vernal 

 migration. The black-poll warbler is one 

 of the best examples. 



the: warblers and cliff swallows 



While the Alaska-breeding robins start 

 off in February, and spend nearly 90 

 days in going from central Missouri to 

 western Alaska, the black-poll warbler 

 remains in his tropical home during Feb- 

 ruary and March, and is not seen in 

 southern Florida until about April 20. 



