"7 8 Loomis on Birds of Chester County., South Carolina. x™ n 



rence during the height of their migration. There are other birds 

 that are uncertain in migration as well as at other seasons, as the 

 Red-breasted Nuthatch here and the American Crossbill in the 

 lower part of the State (Wayne, Auk, IV, pp. 2S7-2S9). This 

 inconstancy seems attributable to a shifting of the lines of move- 

 ment so that these localities are reached in some years and not 

 in others. Both species are of local distribution in the breeding 

 season here at the South, being confined apparently to the higher 

 mountains. The irregularity reported by Dr. Cooper (Proc. 

 U. S. Nat. Mus., II, p. 243) in Lawrence's Goldfinch, Lazuli 

 Bunting, and Western Bluebird seems but further illustration 

 of variability in location of isolated communities. Additional 

 instances in Chester County in winter appear to be afforded in 

 the Short-eared Owl, Purple Finch, Pine Siskin, Towhee, Palm 

 Warbler, and Brown Creeper. In the breeding season the ten- 

 dency to variability is not so great as in winter ; witness the Robin 

 in this locality. The Passenger Pigeon exemplifies variability in 

 a high degree. Where there are great numbers food doubtless 

 enters as an immediate factor in their movements, their erratic 

 mode of migration being accentuated by necessity of continually 

 seeking new feeding grounds. Fear of persecution probably 

 causes them to avoid many localities, particularly in the location 

 of their 'nestings.' 



Where there has been no great change wrought in the face of 

 a region, it is an open question whether much of the alleged 

 extension of range of birds may not be simply shifting of isolated 

 communities within ordinary limits of habitat. 



Sttmmary. — In species of uncertain occurrence in the height of 

 migration, irregularity in breeding or winter residence that can- 

 not be attributed to severity or mildness of season or to failure of 

 food is ascribed to variation in lines of movement (facilitated by 

 local distribution), the migration being regularly performed, but 

 routes varying so that the same localities are not visited every 

 season; in species of habitual occurrence in the height of migra- 

 tion, such irregularity is ascribed to variation in location of 

 isolated communities at extremes of habitat — the birds in both 

 cases not being sufficiently abundant to populate the whole 

 region embraced within their range, thus necessitating choice of 

 abode, which often results in absence in localities that have been 

 favored in other seasons. 



