FAMILY LARID^. GULLS AND TEKNS. 



41 



SUB=FAMILY 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, smalt, but well developed. 



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



Forehead, white; bill, blaok ; imderparts, white; b.'ick, 

 peni-l gray; crowu, black (adult iu summer) ; back and crown, 

 mottled (immature). Sterna antillarmn. Least Tern. 



■See ^'0. 48. 



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



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

 dusky; rest of head, white (immature). Hi/drochelidon nigra suriiiamcnsix. Black Tern. 



See No. .51 . 



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



Outer tail feathers, pure white. 

 Inner web of outer tail feather, graj'. 



Sternn dnvijalli. Roseate Tern. 



See No. 47. 



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; Ijack, pearl gray; breast, 

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



Sterna hirnndo. Common Tern. Wilson's Tern. 



See No. 4.5. 



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

 white; bill iu adults, black, slightly yellowi-sh at tip. Sterna fnrsteri. 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 dejugaUi. Roseate Tern. 



See No. 47. 



' For directionri for measurement, Bee page 9. 



