eS GULLS. 



b^. 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. 



ci. Bill over 2-00 42. Glaucous Gull. 



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, 

 ai. Wing over 17-50 ; depth of bill at nostril over -70. 



47. Black-backed Gull (Ini.). 

 a^. 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. 



fti. Bill under 2-00 43. Iceland Gull (Im.), 



J2. Bill over 2-00 42. Glaucous Gull (Im.). 



II. Wing under 15-00. 



1. Tail pure white. 



A. Head and throat slaty black. 



a. Outer primary black or mostly black. 



ai. 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. 



b^. Tip of first primary white 59. Franklin's Gull. 



J2. Tip of first primary black 60. Bonaparte's Gull. 



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



a. Wings white 39. Ivory Gull. 



b. Primaries with more or less black. 

 bK Wing over 11 00. 



b^. Hind toe very small, without a nail ... 40. Kittiwake. 



63. Hind toe normal, with a nail ... 54. Ring-billed Gull. 



ci. Wing under 11-00 61. Ross's Gull. 



2. Tail marked with black. 

 A. Wing over 13-25. 



a. Primaries mostly white 39. Ivory Gull (Im.). 



b. Primaries black or mostly black . 54. Ring-billed Gull (Im.). 

 £. Wing under 13-25. 



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



b. Hind toe normal, with a nail. 



b^. Tarsus 1-50 or over 58. Laughing Gull (Im.). 



c^. Tarsus under 1-50. 

 t-a. Secondaries pearl color, tail square. 



60. Bonaparte's Gull (Im.). 

 c3. Secondaries mostly white, tail rounded. 



61. Ross's Gull (Im.). 



39. Gavia alba ( Gunn.). Ivory Gull. Ad. — Entire plumage pure 

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



