INDEX TO KEY. 



Family LARID^. Gulls and Terns. 



Subfamily LARINi^. 



Tail, usually nearly square. 



Gulls. 



Group 1. Wing, q.50 to ii inches long 

 Group 2. Wing, 11 to 13 inches long . 

 Group 3. Wing, 13 to 15 inches long . 

 Group 4. Wing, 15 to 17 inches long . 

 Section 1. Length, over 21; bill, over 



See page 43. 

 44- 



" " 44- 



" " 45- 

 2; under parts, white See page 45 



Section 2. Length, over 21 ; bill, over 2; under parts, not white 

 Section 3. Length, over 2 1 ; bill, under 2 ; under parts, white . 

 Section 4. Length, over 2 1 ; bill, under 2 ; under parts, not white. 

 Section 5. Length, under 21 . 

 Group 5. Wing, over 1 7 inches long ...... 



Subfamily STERNINiE. 



Tail, usually forked. 



Terns. 



Group 1. 



Group 2. 



Group 3. 



Group 4. 



Group 5. 



Group 6. Wing, 13 to 17 inches long 

 Group 7. Wing, over 17 inches long 



Wmg, 5.50 to 7.50 inches long 

 Wing, 7.50 to 8.50 inches long 

 Wing, 8.50 to 9.50 inches long 

 Wing, 9.50 to 1 1 inches long . 

 Wing, II to 13 inches long . 



See 



47- 

 48. 

 48. 

 48, 

 48. 

 49- 

 49- 



42 



