FAMILY LARID^E. GULLS AND TERNS. 41 



SUBFAMILY STERNIN/E. 

 Terns. 



Upper mandible, nearly straight, not hooked or decid- 

 edly rounded near tip ; outer tail feathers, usually longer 

 than middle feathers; toes, four; front toes, webbed; 

 hind toe, small, but well developed. 



* Group 1. Wing, 5.50 to 7.50 inches long. 



Forehead, white; bill, black; underparts, white; back, 

 pearl gray; crown, black (adult iu summer) ; back and crow-n, 

 mottled (immature). Sterna antillarum. Least Tern. 



See No. 48. 



* Group 2. Wing, 7.50 to 8.50 inches long. 



Head and underparts, black (adult) . A patch of black behind the eye ; back of head, 

 dusky; rest of head, white (immature). Hijdrochelidon nigra surinamensis. Black Tern. 



See No. 51. 



* Group 3. Wing, 8.50 to 9.50 inches long. 



Outer tail feathers, pure white. Sterna dougalli. Roseate Tern. 



See No. 47. 



Inner web of outer tail feather, gray. Sterna forsteri. Forster's Tern. 



See No. 44. 



* Group 4. Wing, 9.50 to 1 1 inches long. 



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

 washed with pearl gray; bill in adults, red, tipped with black; tarsus, usually over .70. 



Sterna hirundo. Common Tern. Wilson's Tern. 



See No. 45. 



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

 white; bill in adults, black, slightly yellowish at tip. Sterna forsteri. Forster's Tern. 



See No. 44. 



Outer tail feather, entirely pure white ; back, pearl gray ; breast, white, often tinged 

 with faint rose color; bill, in adults, black with basal portion, red. 



Sterna dougalli. Roseate Tern. 

 See No. 47. 



* For directions for measurement, see page 9. 



