36 KEY TO THE BIRDS OF EASTERN NORTH AMERICA. 



FAMILY LARID/E. 

 Gulls and Terns. 



SUB-FAMILY LARIN/E. 

 (lulls. 



Upper mandible, curved ; unguis (end of bill), not swollen; middle tail 



feathers, about equal in length to the others ; 

 tail, rarely dark, although sometimes tipped 

 with black or brown ; hind toe, small, but 

 always present except in one genus ; bill, with- 

 out cere. 



* Group 1. Wing, 9.50 to 11 inches long. 



Underparts, white; inuer web of first primary, white, with black spot near the end; the 

 tip, white; shaft of feather, white; adult birds have the bill dark red ; in immature birds 

 it is brownish. Larus franklinii. Franklin's Gull. 



See No. 34. 



Underparts, white ; inner web of first primary, white ; the tip, black ; bill, black ; shaft 

 of feather, white. Larus Philadelphia. Bonaparte's Gull. 



See No. 35. 



Underparts, white; inner web of first primary, about half white; shaft of feather, 

 dark brown on upper surface. In the adult the bill is black, tipped with yellow. 



Xema sabinii. Sabine's Gull. 



See No. 38. 



* Group 2. Wing, 1 1 to 13 inches long. 



Shafts of primaries, black or dark brown; underparts, not pure white (immature). 



f Larus atricilla. Laughing Gull. 

 See No. 33. 



Underparts, pure white; inner web of first primary, white, with black spot near the 

 end, the tip, white ; shaft of feathers, white. Adult birds have bill dark red ; in immature 

 birds it is brownish. Larus franklinii. Franklin's Gull. 



See No. 34. 



* For directions for measurement, see page 9. 



