[39] 



A further hindrance to the more exact definition of faunal lines 

 is, as Professor Allen says, that rarely is any species limited to a 

 narrower area tiian that of two or three faunae and hence that 

 tliese are determined by the peculiar association of species and 

 not by the range of a singrle or of a few "restricted" species. 



With regard to the influence of longitude, although the 

 western boundaries of these founas extend to the limits ot what 

 has been called by Prof. Baird, the Eastern Province, which is 

 bounded approximately by the meridian of ioo°, the Appalach- 

 ian Mountains forming but a feeble barrier ornithologically, 

 there is still a slight change in the characters of the faunae as 

 soon as we proceed westward of this range, many species be- 

 coming abundant that are rare at the east and vice versa and we 

 may expect to find some of the birds of the Mississippi and 

 Ohio valleys extending their migrations into the Trans-Appa- 

 lachian region of tlie Virginias, especially along the rivers, like 

 the Kanawha and Big Sandy. More investigations are needed 

 upon this point, but the observations of Messrs. Scott and 

 Brewster, who found ^uiscalus quiscula oeneus^ Geothlypis 

 formosa and Dendroica cccrulea^ becoming more common in the 

 localities examined by them, than they are east of the mountains 

 would seem to indicate that this is the case. 



The times of arrival and departure of the migratory birds of 

 course varies somewhat in different localities in the Virginias, 

 but the height of the spring migratory season appears to be about 

 that given by Drs. Coues and Prentiss for the District of Colum- 

 bia, viz. : from April 30th to May 30th. This period is on the 

 whole in accordance with my own observations carried on for 

 some time in Albemarle County and also with some of the West 

 Virginia records. Mr. Freke's dates of arrival for Amelia 

 County seem to me in many instances late. 



The limits of the autumn migration are not quite so sharply 

 defined as is the case in spring, doubtless partially due to the 

 fact that the young and old often migrate separately and it is 

 spread over a more extended period, many species lingering 

 longer than at the latter season, but the great mass of migra- 

 ting birds are met witli between September ist and October 15th. 



