1874.] 309 [Ridgway. 



Carolinian Fauna, although the latter appears to be very rare east of 

 the Alleghanies. 



The extremes of temperature in winter and summer, which are 

 perhaps greater in the Mississippi Valley than in corresponding lati- 

 tudes of the Atlantic States, no doubt explain why the northern 

 species extend so much farther south and the southern ones so much 

 farther north, in their respective seasons of migration, in the former 

 region than in the latter. In short, there are more northern birds in 

 winter and more southern ones in summer. The sedentary fauna 

 associates in summer with one possessing a decided subtropical im- 

 press, while in winter it mingles with the arctic series. The resident 

 Cardinalis virginianus, Loplioplianes bicolor, Parus carolinensis, Thry- 

 othorus ludovicianus, T. bewicki and Centurus carolinus associate in 

 summer with Cyanospiza ciris, Guiraca ccerulea, Peucoea cestivalis, 

 Protonotaria citrea, Dendroica dominica, Conuriis carolinensis, An- 

 trostomus carolinensis, Campepldlus principalis, and such southern 

 forms, while their winter companions are JEgiothus linaria, Loxia 

 americana, L. leucoptera, Plectrophanes lapponicus, P.pictus, P. niva- 

 lis, Pinicola canadensis, etc.; Astur atricapillus, Nyctea scandiaca 

 and Nyctale acadica, may be seen in winter, where in summer Astur- 

 ina plagiata, Ictinia mississippiensis , Nauclerus forjicatus, Elanus 

 leucurus, and Sirix pratincola replace them. There is likewise an 

 extensive overlapping of the western and eastern fauna?, since the 

 eastward extension of the Missouri plains, in the modified form of the 

 Illinois prairies, causes many of the western species to range as far 

 at least as the Wabash River. The eastern species pass them and 

 reach as far west as the Missouri River — many of them to the Rocky 

 Mountains, or even well into that range itself. 



The western element in the Illinois bird-fauna is thus rendered con- 

 spicuous by the abundance of Chondestes grammaca, Collurio excubiio- 

 roides arid EremopMla atyestris, which breed plentifully almost every- 

 where; Vireo bellii is common, locally, even on the most eastern 

 prairies in the State; Sturnella neglecta is sparingly scattered over the 

 same area, while on those of the central and western portions Spizella 

 pallida is found. Xanthocephalus icterocepliaJus is common, even 

 abundant, in suitable sections, nearly throughout the State ; Helmin- 

 thophaga celata is abundant in the Wabash Valley during both the 

 spring and fall migrations. Scolecophagus cyanocephalus is occasional 

 in winter, while Falco polyagrus and Buteo swainsoni occur irregu- 



