8 Campbell, Dichotomous Key. 



48. Lower edge of lower bill horn colour (head dark grey, bill brownish- 



black in youth). T. cuhninatiis (Flat-billed Albatross). 



Base only and not lower edge of bill yellow. 



T. chlororhynchiis (Yellow-nosed Albatross). 



49. Three toes webbed, hind toe free . . . . . . . . 50 



All four toes united one to the other by webs . . . . . , 91 



50. Upper beak sharp and straight or hooked . . . . . . 51 



Upper beak flattened and with nail-like tip. Ducks. 73 



51. Claws feeble ; bill without membrane (cere) at base . . . . 52 

 Claws large and hooked ; bill with naked cere at base. Skuas. 71 



52. Both mandibles about equal in length and slender. Terns. 53 

 Upper mandible hooked over lower. Gulls. 70 



53. Outside tail feathers longest . . . . . . . , . . 54 



Outside tail feathers shortest . . . . . . . . 64 



54. Tarsus short comparatively . . . . . . .... 55 



Tarsus very slender, 1.6 inches long. 



Gelochelidon anglica (Gull-billed Tern). 



55. Bill slender ; tail half length of wing. Sterna. 56 

 Bill very stout (red) ; tail less than half wing. 



Hydroprogne caspia (Caspian Tern). 



56. Total length not more than 14 inches ; wing to 9 inches . . . . 57 

 Total length 14 to 20 inches ; wing 10 to 14 inches . . . . 59 



57. Crown black in breeding plumage ; forehead white, bill and legs 



yellow . . . . . . . . . . . . 58 



Crown always white ; nape of neck black ; bill and legs black. 



S melanauchen (Black-naped Tern). 



58. Lores white. 5. nereis (White-faced Ternlet). 

 Lores black. 5. sinensis (White-shafted Ternlet). 



59. Back and rump umber or black . . . . . . . . 60 



Back and rump pale to dark grey . . . . . . . . 61 



60. Back and rump umber (under parts white in young). 



S. ancestheta (Panayan Tern). 

 Back and rump black (under parts dark brown in young). 



S. fidiginosa (Sooty Tern). 



61. Forehead black to base of beak . . . . . . . . 62 



Forehead white ; crown black (mottled white when immature) 63 



62. Pale grey above ; rose tinge on white breast ; wing 9.3 inches ; 



bill orange (black in youth) ; legs red. 



S. doiigalli (Roseate Tern). 



Plumage grey above ; wing 12 inches ; bill orange or red ; legs 



black. S. media (Lesser Crested Tern). 



63. Bill greenish- yellow ; legs blackish ; wing 14 inches 



5. bergii (Crested Tern). 

 Bill black ; legs red ; wing 11. 3 inches. 



5. frontalis (White-fronted Tern). 



64. Plumage white or white and grey . . . . . . . . 65 



Plumage grey or chocolate-brown or sooty . . . . . . 67 



65. Plumage pure white. ^^Vgw Candida (White Tern). 

 Upper surface grey ; cap and flanks black. Hydrochelidon. 66 



66. Wing 9.5 inches. H. hybrida (Marsh Tern). 



