34^ 



Cooke, Effect of Altitude on Bird Migration. 



TAuk 

 Ljuly 



In addition there are three specie.s that move much more 

 slowly ; the Yellow-throated Warbler appears at Raleigh March 

 26 and is not seen at Asheville until April 21, a difference of 26 

 days. The corresponding dates for the Maryland Yellow-throat 

 are March 30 and April 18, a difference of 19 days. For the 

 White-eyed Vireo the times of arrival are April 2 and April 15, a 

 difference of 13 days. These three are all early migrants, and it 

 is true in general that the earlier a species moves northward in 

 the spring the slower will be its average daily advance. All three 

 find near Asheville their highest extension into the mountains, and 

 it is possible that this fact may account for their delayed arrival. 

 Though when birds are migrating in a level country the opposite 

 is true, — they migrate more rapidly as they approach the northern 

 limit of their range. 



The most interesting phase of the comparison of migration at 

 the two localities is connected with the time of arrival of the 

 following species : 



m 



