2D Loomis on Birds of Chester County, South Carolitia. \ T " 



Ljan. 



A FURTHER REVIEW OF THE AVIAN FAUNA 

 OF CHESTER COUNTY, SOUTH CAROLINA. 1 



by leverett m. loomis. 



Concluding Observations on Migrations.' 2 



The conclusions reached in this portion of the article, while 

 based on the observations of fourteen years in Chester County, 

 South Carolina, have been tested and corroborated by the facts 

 bearing upon the migration of North American birds found 

 throughout the literature, and by a study of the earlier southward 

 movements at Monterey Bay, California, from the latter part of 

 June to near the end of August, 1S92. 



/. Variability in the Occurrence of Transient Migrants. 



Variability in the occurrence of transient migrants in a given 

 locality maybe said to be of two sorts, that which is periodic and 

 that which is erratic. 



Periodic Variability. — This is illustrated in such birds as 

 habitually occur more sparingly in this region in the southward 

 migration than in the northward, and vice versa: examples, the 

 Bobolink and Yellow Palm Warbler, most abundant in spring, 

 and the Chestnut-sided, Blackburnian, and Palm Warblers, most 

 abundant in autumn. Such seasonal variation in abundance can 

 be explained only in two ways, either the majority pass to one 

 side or else they pass over without stopping. It seems highly 

 improbable that smaller land birds of abundant and extended dis- 

 tribution uniformly pass directly over this locality without being 

 fairly represented in some stage of their movement, for it appears 

 hardly possible that there should be so nice an adjustment of suc- 



1 Concluded from Vol. VIII, pp. 49-59, 167-173, and Vol. IX, pp. 28-39. 



2 Read in part before the Eleventh Congress of the American Ornithologists' Union 

 held in Cambridge, Mass., Nov. 21-23, x 893- 



