° s " . I Loomis on Birds of Chester County, South Carolina. \OT. 



of June. The first Snowflakes, however, appeared in April 

 before the snow had really begun to melt and the King Eiders 

 before there was any open water except the shifting 'leads' at a 

 distance from the shore. Migration closes in Chester County 

 about June i, the decline being evident after the first week of 

 May. It is significant that Mr. Scott reports boreal Sandpipers 

 and Plovers in Florida as late as the first and second weeks of 

 June (Auk, VI, pp. 156-159). 



It will be observed that the repopulation of the continent 

 occupies about the same length of time as the depopulation, 

 nearly half the year. 



Northward movement seems clearly not the starting point of 

 migration. The first migration in all North American birds 

 must be the southward. Evacuation is necessitated by winter, 

 and as soon as the pressure of winter is in any measure relieved 

 the return begins. At no time is there a beginning in the north- 

 ward movement like that of the southward. The commence- 

 ment of the southward and the ending of the northward movement 

 are sharply defined, but the ending of the southward and the 

 beginning of the northward are merged into each other — the 

 two movements being contemporaneous for several months, the 

 northward only achieving the supremacy after the repelling forces 

 of winter have ceased to be potential. In brief, southward migra- 

 tion is esteemed to be enforced departure, and northward 

 migration to be the earliest possible return of the birds to their 

 home, to the region of their birth. Before pursuing this aspect 

 of the subject further it is necessary to define the relation between 

 cold and food-supply as affecting the later southward and earlier 

 ■northward movements. 



The abrupt departure of the bulk of Mockingbirds with the 

 first cold snap in autumn (Auk, IX, p. 39) would seem to 

 indicate that they -find the cold uncongenial, and therefore 

 migrate. On the other hand the fact that thev are common 

 winter residents in spite of the vicissitudes of weather seems to 

 indicate that cold alone is not the cause of their migration. 

 Many other species that are common or even abundant through 

 winter are most numerous in spring and fall ; the Flicker, Blue 

 Jay, Meadowlark, and Myrtle Warbler being examples. It has 

 been suggested that the more northern-born individuals of a 



