° 1920 ] Averill, Migration and Physical Proportions. 577 



Dendrotca V. Breeding S. of Canadian Zone. Not reaching 

 S. America in winter. 

 Prairie 

 Kirtland's 

 Pine 



Yellow-throated 

 Chestnut-sided 



Average 



Jamaica Yellow 



Guadaloupe 



Panama 



Adelaide's 



Santa Lucia 



Cuban 



Vitelline 



Plumbeous 



Streaked 



Average 



Taking the genus Dcndroica the difference is almost entirely 

 in wing length, the tail does not differ as it does when comparing 

 geographical races, nor do the bill and tarsus differ much. 



In this genus as in the others preceding we can certainly " pick 

 the winner" by relative length of wing and tail. The Blackpoll 

 is one of the most famous of all passerine birds as a migrant. 

 Quoting from Cooke " the shortest journey any blackpoll performs 

 is 3500 miles while those that nest in Alaska have 7000 miles to 

 travel to their probable winter home in Brazil" and we find it 

 showing the maximum difference between length of wing and 

 tail 22.9. The Bay-breasted, Blackburnian and Yellow Warbler 

 all of which reach South America in their flight show a difference 

 of 20.3, 19.5 and 18.1 respectively. 



We note that the Cerulean Warbler although it does not go 

 far north is well proportioned for flight (difference 20.5) and it will 

 be found that the shorter winged species neither go far north nor 

 to South America. 



I have tabulated measurements for birds of other families and 

 the same principle seems to hold good in nearly every case, though 



