68 GULLS. 



^3. 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. 



cK 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 (Im.). 

 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. 



bK 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. 

 a2. 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, 



b^. Tip of first primary black (30, Bonaparte's Gull. 



£. 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. 



?>2. Hind toe very small, without a nail . , . 40. Kittiwake. 



*3. Hind toe normal, with a nail , . , 54, Eing-billed Gull, 



(i. Wing under 11-00 61, Eoss'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, Eing-billed Gull (Im,). 



B. 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,). 



<;!. Tarsus under 1-50. 

 c'2. Secondaries pearl color, tail square, 



60. Bonaparte's Gull (Im,). 

 c3. Secondaries mostly white, tail rounded, 



61. Eoss's Gull (Im.). 



39. Gavia a.lba> ((?unn.). Ivory Gull. Ad. — Entire plumage pure 

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



