78 



TERNS. 



mostly or entirely white ; a black space generally on the side of 



the head inclosing the eye (59. FOKSTER'S TERN (Tin.). 



J 2 . Outer web of outer tail-feather darker than inner web ; tarsus 



over -70 TO. COMMON TERN (Im.). 



b a . Outer web of outer tail-feather darker than inner web; tarsus 



under -70 71. ARCTIC TERN (Im.). 



B. Wing blackish, over 9-00. 



a. Under parts blackish 75. SOOTY TERN (Im.). 



b. Under parts white 76. BRIDLED TERN (Im.). 



4. Crown silvery gray ; lores black ; rest of plumage sooty black. 



79. NODDY. 

 II. Wing over 13-00. 



A. Wing 15-00 or over; outer primary mostly gray. 64. CASPIAN TERN. 



B. Wing under 15-00 ; inner half of inner web of first primary white. 



65. KOYAL TERN. 



FIG. 61. First primaries of adult Terns, seen from below, (a) Caspian Tern ; 

 (b) Royal Tern ; (c) Common Tern ; (d) Arctic Tern ; (e) Roseate Tern. 



63. Gelochelidon nilotica Ihmelq. GULL-BILLED TERN; MARSH 

 TERN. Ad. in summer. Top of the head and nape black; back and wings 

 pale pearl-gray; outer web of outer primaries silvery; tip and shaft part of 

 the inner web darker ; inner part of the inner web, except for a narrow mar- 



