INDEX TO KEY. 



Family LARID^^. Gulls and Terns. 



Subfamily LARIN.^. Gulls. 



Tail, usually nearly square. 



Group 1. Wing, Q.50 to 1 1 inches long See page 43. 



Group 2. Wing, 11 to 13 inches long . " " 44- 



Group 3. Wing, 13 to 15 inches long . " " 44- 



Group 4. Wing, 15 to 17 inches long . " " 45. 



Section 1. Length, over 21; bill, over 2; under parts, white See page 45 

 Section 2. Length, over 21; bill, over 2; under parts, not white " 45 

 Sections. Length, over 21; bill, under 2; under parts, white . " 46 

 Section 4. Length, over 2 1 ; bill, under 2 ; under parts, not white. " 46 

 Sections. Length, under 2 1 . ......" 46 



Group 5. Wing, over 17 inches long . . . . . " 47 



Subfamily STERNINiT. Terns. 



Tail, usually forked. 



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 p. 47. 

 48. 

 48. 

 48. 

 48. 



49- 

 49. 



42 



