Vol. XXII 

 1904 J 



Eaton, Sfring Bird Migration, igo^- 



341 



Each of these species appears at Asheville, in the mountains, 

 before being seen at Raleigh, on the plains. The probable expla- 

 nation of this anomaly is that each of these species breeds com- 

 monly at Asheville, and rarely or never at Raleigh. There is 

 here a striking and unexpected exemplification of the rule that the 

 southermnost breeding birds constitute the van in spring migration. 

 While the present sum of knowledge is not sufficient to warrant 

 the statement that this rule is universal, and very likely further 

 investigation will show some exceptions, yet the above facts furnish 

 strong evidence in its favor. 



SPRING BIRD MIGRATIONS OF 1903. 



BY ELON HOWARD EATON. 



Bird migration is a very elusive subject. At least we have 

 found it so in western New York, after trying for years to deter- 

 mine its times and seasons, bird routes and isopiptoses, causes and 

 results. Even if one could be everywhere all the while at the same 

 time, it would be difficult to run down the last factor in this com- 

 plex problem. Meanwhile we are after facts. 



The writer has been greatly disappointed to find how imperfect 

 are the records of observers in determining the presence of a bird 

 at any given station, rendering it almost impossible to draw cor- 

 rectly the lines of simultaneous arrival. Consequently at Roches- 



