FAMILY LARID^E. GULLS AND TERNS. 43 



Outer web of outer tail feather, darker than inner web; back, pearl gray; breast 

 and underpart?, pearl gray; bill, in adults, entirely red; tarsus, usually less than .70. 



Sterna paradiscea. Arctic Tern. 



See No. 46. 



Back, black ; a white stripe from forehead, extending over the eye ; breast, white ; bill, 

 in adults, black. Sterna fuliyinosa. Sooty Tern. 



See No. 49. 



Back, sooty or grayish brown; a white stripe from forehead, not reaching above the 

 eye ; bill, black. Sterna ancethetus. Bridled Tern. 



See No. 50. 



Back, sooty brown; uuderparts, sooty brown. Anous stolidus. Noddy Tern. 



See No. 53. 



* Group 5. Wing, 11 to 13 inches long. 



Bill, black, not tipped with yellow; feet, blackish; back, pearl gray ; bill, comparatively 

 short and stout. Gelochelidon nilotica. Gull-billed Tern. 



See No. 39. 



Bill, black, not tipped with yellow; feet, black; back, black or sooty. 



Sterna fuliginosa. Sooty Tern. 

 See No. 49. 



Bill, red, tipped with black; feet, orange red; back, pearl gray or gray and buff. 



Sterna hirnndo. Common Tern. Wilson's Tern. 



See No. 45. 



Bill, black, tipped with pale yellow; feet, dark; bill, comparatively long and slender. 



Sterna sandvicensis acuflavida. Cabot's Tern. 

 See No. 39. 



* Group 6. Wing, 13 to 17 inches long. 



Bill, orange or yellowish ; tarsus, less "than 1.50; inner web of outer primary, usually 

 with more or less white. Sterna maxima. Royal Tern. 



See No. 41. 



Bill, red or reddish; tarsus, over 1.50; inner web of outer primary, usually without 

 white. Sterna caspia. Caspian Tern. 



See No. 40. 



Bill, black, tipped with yellow. Sterna sandvicensis acuflavida. Cabot's Tern. 



See No. 39. 



* Group 7. Wing, over 17 inches long. 



Bill, red or reddish. Sterna caspia. Caspian Tern. 



See No 40. 



* For directions for measurement, see page 9. 



