40 



KEY TO THE BIRDS OF EASTERN NORTH AMERICA. 



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



not white. 



Outer webs of priniaries, dark 1)rowii; bill, over 1.00 (immature). 



Laritx ar(irnt.(ttns siiiithsoninmis. American Herring Gull. 



See No. 30. 



Outer \vel)s of primaries, brownish; bill, under l.HO (immature). 



Lams knmlieni. Kumlien's Gull. 



See No. 26. 



Outer we1>s of i)rimaries, asli color (innnature). 



Larvs Irneopterns. Iceland Gull. 



See No. 25. 



Section 5. Length, under 21. 



A band of blaek on the bill (adult). 15111, didl yellow, tipped with black (immature"). 



Lams delawarrnsis. Ring=billed Gull. 

 See No. 31. 



Tcrnb. 



Gulls. 



-X- 



Group 5. Wing, over 17 inches long. 



Primaries, m:irk(>d with moi-(! or less black. Lams marinns. Great Black=backed Gull. 



See No. 27. 



No bliK'k on primaries. Lams {/Jaiims. Glaucous Gull. 



See No. 24. 



* For dii'i'ctions for measurement, see page 9. 



