68 GULLS. 



6. Primaries pearl-gray, tipped with white, and with well-defined 

 gray spaces on the outer webs of the two outer primaries and on 

 both webs of the third and fourth primaries. 



45. KUMLIEN'S GULL. 



c 1 . Bill over 2-00 42. GLAUCOUS Gn.u 



C. Back grayish, whitish, or brownish, or mottled or spotted with gray- 

 ish or brownish. 



a. Tail black or blackish, with or without irregular white markings. 

 a 1 . Wing over 17'50; depth of bill at nostril over '70. 



47. BLACK-BACKED GULL (Im.). 

 a s . Wing under 17'50 ; depth of bill at nostril under -70. 



51a. AM. HERRING GULL (Im.). 51. HERRING GULL (Im.). 



b. Tail white or whitish or grayish brown, with or without black 

 markings. 



b l . Bill under 2-00 43. ICELAND GULL (Im.). 



IP. Bill over 2-00 42. GLAUCOUS GULL (1m.). 



II. Wing under 15-00. 



1. Tail pure white. 



A. Head and throat slaty black. 



a. Outer primary black or mostly black. 



a 1 . Outer primary entirely black .... 58. LAUGHING GULL. 

 a*. Inner half of inner webs of first primary white. 



62. SABINE'S GULL. 



b. Outer primary mostly white. 



A 1 . Tip of first primary white 59. FRANKLIN'S GULL. 



i". Tip of first primary black 60. BONAPARTE'S GILL. 



B. Head white, sometimes washed with pearl-gray. 



o. Wings white 39. IVORY GULL. 



b. Primaries with more or less black. 

 6". Wing over 11 00. 



i a . Hind toe very small, without a nail ... 40. KITTIWAKE. 



6 s . Hind toe normal, with a nail ... 54. KINO-BILLED GILL. 



c. Wing under 11-00 61. Ross's GULL. 



2. Tail marked with black. 

 A. Wing over 13-25. 



a. Primaries mostly white 39. IVORY Gru. (ImA 



b. Primaries black or mostly black . 54. KINO-BILLED GULL (Im.). 

 Ji. Wing under 13-25. 



a. Hind toe very small, without a nail . . . 40. KITTIWAKK (Im.). 



b. Hind toe normal, with a nail. 



/>'. Tarsus 1-50 or over 58. LAUGHING GULL (Im.). 



c 1 . Tarsus under 1-50. 

 <*. Secondaries pearl >-nlr. tail square. 



60. BONAPARTE'S GULL (Im.). 

 c*. Secondaries mostly white, tail rounded. 



61. Ross's GULL (Im.). 



39. Gavia alba !n mi.). IVOKY GM.I.. .(</. Kntire plumage pure 

 white; bill yellow, feet black. //.-- Similar to ad., but the wing and tail 



