40 



BULLETIN 185, U. S. DEPARTMENT OF AGRICULTURE. 



judgment in regard to members of other groups. Thus, although a cer- 

 tain general tendency is observable, each species presents a separate 

 problem, to be solved for the most part only by patient, painstaking 

 observation. 



^ BREEDING RANGt 



M WINTER HOME 

 ,« EAST AND lA^EST LIMITS 

 OE MIGRATION ROUTE 



Fig. 18. — Distribution and migration of ttie red-eyed vireo ( Vircosylva oUvacca). An example of a lately 

 extended breeding range and migration route. It is evident that the species has only recently invaded 

 Washington by an extension almost due west from the northern Mississippi Valley, and that it still 

 migrates spring and fall along the route originally traversed in this extension. (See p. 37 and also fig. 19.) 



RELATIVE POSITION DURING MIGRATION. 



Spring migration has its own special features, and no such syn- 

 chronous movement then occurs as has been described as "normal 



