154 



GULLS 



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.). 



B. Wing under 13'25. 



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



b. Hind-toe normal, with a nail. 



b 1 . Tarsus 1'50 or over 58. LAUGHING GULL (Im.), 



c 1 . Tarsus under 1*50. 



c 2 . Secondaries pearl color, tail square. 



60. BONAPARTE'S GULL (Im.), 

 c 3 . Secondaries mostly white, tail rounded. 



61. Ross's GULL (Im.) 



FIQ. 78. First primaries of adult Gulls, seen from below: (a) Herring Gull; (6) Ring- 

 billed Gull; (c) Laughing Gull; (d) Franklin's Gull; (e) Bonaparte's Gull. 



39. Pagophila alba (Gunn.). IVORY GULL. Ads. Entire plumage 

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

 feathers, and sometimes wing-coverts, with a black spot at their tips. L., 

 17-00; W., 13'25; T., 5*50; B., 1'35. 



Range. Arctic seas. Breeds in high Arctic latitudes from Melville 



