36 KEY TO THE BIRDS OF EASTERN NORTH AMERICA. 



FAMILY LARID^. 

 Gulls and Terns. 



SUB=FAM1LY LARIN^. 

 Gulls. 



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. 



Uuderpjirts, white; iiiiuT wcl) of first priinaiy, white, with bhick spot ue:ir the eud; the 

 tip, white; shaft of feather, white; adult birds liave the bill dark red ; iu ininiature liirds 

 it is 1)rownish. Lams frankUnii. Franklin's Gull. 



See No. ;W. 



Utiderparts, white; inner web of first primary, white; the tip, black; bill, black; sliaft 

 of feather, white. Lams Philadelphia. Bonaparte's Qull. 



See No. 35. 



Uuderparts, white; inner web of first i^rimary, about half white; shaft of feather, 

 dark brown on upper surface. In the adult the bill is l)lack, tipped with yellow. 



Xcma sahinii. Sabine's Gull. 



See No. 38. 



* Group 2. Wing, 11 to 13 inches long. 



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



Larus atricilla. Laughing Gull. 

 See No. 33. 



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

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

 birds it is brownish. Lams frankUnii. Franklin's Qull. 



See No. 34. 



* For directions for measurement, see page 9. 



