574 



Averill, Migration and Physical Proportions. 



rAuk 

 |Oct. 



the male bird always. The first column contains the name of 

 the bird, the second a brief statement of its range, the third the 

 wing length, the fourth the tail length, the fifth column the differ- 

 ence between wing and tail lengths. It is this column that shows 

 at a glance that the bird making the long migration, is also best 

 proportioned for flight. Measurements in millimeters. 



Helminthophila. 



Here we see by the figure opposite the Tennessee Warbler, 

 22.1, that it is the bird making the longest migration. At the 

 end of the list is the Dusky Warbler, 9.4, showing the longest 

 tail of all and the shortest wing relatively. We notice that it 

 carries a larger bill and tarsus than the Tennessee in accordance 

 with what we have already said. 



In the same way we may compare the Orange-crowned, Lutes- 

 cent and Dusky, three races of the same species and note the better 

 flying characteristics of the two birds that reach Alaska. 



Let us in the same way make a table of the genera Oporornis 

 and GcothJypis. 



These six birds are arranged in order of their relative wing and 

 tail lengths. With the exception of the Kentucky they also come 

 in order of the extent of their migratory range. While the tail 

 and wing vary greatly the bill and feet remain very much alike 



