INDEX TO KEY. 



Family LARID^. Gulls and Terns. 

 Subfamily LARIN^. Gulls. 



Tail, usually nearly square. 



GROUP 1. Wing, 9.50 to n inches long 

 GROUP 2. Wing, n 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 2; under parts, white 



See page 43. 



" " 44- 

 " " 44- 

 " " 45- 



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 . 

 GROUPS. Wing, over 1 7 inches long .... 



45- 

 46. 

 46. 

 46. 

 47- 



Subfamily STERNIN^. Terns. 



Tail, usually forked. 



GROUP 6. 

 GROUP 7. 



GROUP 1. 



GROUP 2. 



GROUP 3. 



GROUP 4. 



GROUP 5. 

 Wing, 13 to 17 inches long 

 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 ri inches long . 

 Wing, ii to 13 inches long . 



See p. 47. 



" 48. 



" 48. 



" 48. 



" 48. 



" 49- 



" 49- 



