40 



KEY TO THE KIRDS OF EASTERN NORTH AMERICA. 



Section 4. Length, over 21 ; bill, under 2; underparts, 



not white. 



Outer webs of primaries, dark l)rowu: bill, over 1. DO (immature). 



Lams niyjcntatns smithsonianus. American Herring Gull. 



See No. 30. 



Outer webs of jiriinarii's. Ijrownish; bill, uuiler l.'.tO (^immature). 



Lams knmlieni. Kumlien's Gull. 

 See No. 26. 



Outer webs of primaries, ash color (immature). 



iMms h'ucoptems. Iceland Gull. 



See No. 25. 



Section 5. Length, under 21. 



A baud of black ou the bill (adult). IViU, dull yellow, tipped witli black (immature"). 



Lams cMaimrcnsis. Ring^billed Gull. 

 See No. 31. 



Terns 



Gulls. 



* 



Group 5. Wing, over 17 inches long. 



I'riinarit's. marked with more or less black. Lams marhnts. Great Black=backed Gull. 



See No. 27. 



No blaek ou ])rimarie 



Lams f/Janrus. Glaucous Gull. 

 See No. 24. 



* For directions for mcasurcmoiit, sec paj^u 9. 



