LIST OF ILLUSTRATIONS. XI 



PAGE 



White-winged Black Tern (Ch. leucopterus), bill. . . . . . . . 693 



Gull-billed Tern (Gelochelidon n. nilotica), bill . . . . . . . . 695 



Caspian Tern (Hydroprogne caspia), bill . . . . . . . . . . 699 



Sandwich Tern (S. s. sandvicensis), head of juvenile . . . . . . 703 



Arctic Tern (S. paradiscea), Common Tern (S. h. hirundo), and Roseate 



Tern (S. d. dougallii), outer tail-feathers of summer adults . . 705 



Arctic Tern and Common Tern, portions of outer primaries . . . . 709 

 Plate 10.— Nestlings in down of : 1, Black Tern (Chlidonias n. niger). 



2, Little Tern (Sterna a. albifrons). 3, Common Tern (S. h. hirundo). 



4, Arctic Tern (S. paradiscea). 5, Roseate Tern (S. d. dougallii). 



6, Sandwich Tern (S. s. sandvicensis) . . . . . . facing 710 



Arctic Tern, head, first summer .. .. .. .. .. .. 713 



Little Tern, head, adult, summer .. .. .. .. .. .. 715 



Sooty Tern (S. f. fuscata), head, adult, summer . . .. .. .. 718 



Sabine's Gull (Xema sabini), tail of juvenile . . . . . . . . 722 



Wedge-tailed Gull (Rhodostethia rosea), head, adult, summer . . . . 724 



Little Gull (Larus minutus), head of juvenile . . . . . . . . 731 



Black-headed Gull (L. r. ridibundus) and Common Gull (L. c. canus), 



wings of adults . . . . . . . . . . . . . . 733 



Two outer primaries of juveniles of Common Gull, Mediterranean 



Black-headed Gull (L. melanocephalus), Black-headed Gull and 



Bonaparte's Gull (L. Philadelphia) . . . . . . . . . . 735 



Mediterranean Black-headed Gull, head, adult, summer . . . . 738 



Great Black-headed Gull (L. ichthy actus), head, adult, summer . . 741 



Common Gull, head, adult, winter . . . . . . . . . . 744 



Herring -Gull (L. a. argentatus), middle tail-feathers of 1st, 2nd and 



3rd winter . . . . . . . . . . . . . . . . 751 



Plate 11. — Nestlings in down of : 1, Herring-Gull (Larus a. argentatus). 



2, Black-headed Gull (L. r. ridibundus). 3, Kittiwake (Rissa t. 



tridactyla). 4, Arctic Skua (Stercorarius parasiticus). 5, Common 



Guillemot (Uria t. troille). 6, Black Guillemot (U. g. grylle). 



7, Razorbill (Alca torda) . . . . . . . . . . facing 752 



Two outer primaries of adults of Yellow-legged Herring-Gull (L. a. 



cachinnans), Herring- Gull (L. a. argentatus) and British Lesser 



Black-backed Gull (L.f. affinis) .. .. .. .. .. 754 



Tips of 8th primaries of juveniles of British Lesser Black-backed Gull 



and Herring-Gull . . . . . . . . . . . . . . 758 



Great Black-backed Gull (L. marinus), 2nd primaries of : 1, juvenile 



and 1st winter. 2, 2nd winter. 3, 3rd winter. 4, adult . . . . 762 



Glaucous Gull (L. hyperboreus) and Iceland Gull (L. glaucoides), heads 766 

 Plate 12. — Some British Gulls in flight, to illustrate differences and 



similarities . . . . . . . . . . . . . . facing 768 



Kittiwake Gull (Rissa t. tridactyla), outer primaries of adult . . . . 771 



Kittiwake Gull, tail of juvenile .. .. .. .. .. .. 772 



Ivory -Gull (Pagophila eburnea), head of juvenile . . . . . . 774 



Great Skua (Stercorarius s. skua), head . . . . . . . . . . 777 



Pomatorhine Skua (S. pomarinus), tail .... . . . . . . 780 



Arctic Skua (S. parasiticus), tails of adult and juvenile . . . . 784 



Long-tailed Skua (S. longicaudus), tail . . . . . . . . . . 788 



Arctic Skua and Long-tailed Skua, bills . . . . . . . . . . 789 



Razorbill (Alca torda), heads, adult winter and 1st winter . . . . 792 



Razorbill, wing of juvenile . . . . . . . . . . . . . . 793 



Razorbill and Guillemot (U. aalge), central tail-feathers . . . . 799 



Northern Guillemot (U. a. aalge) and Brunnich's Guillemot (U. I. 



lomvia), heads, adult, winter . . . . . . . . . . . . 800 



Black Guillemot (U. g. grylle), wings of adult and 1st winter . . . . 803 



Little Auk (Alle alle), head of adult winter 806 



Southern Puffin (Fratercula a. grabce), heads of adult summer, adult 



winter, and juvenile . . . . . . . . . . . . . . 809 



Great Bustard (Otis t. tarda) head, male adult, summer . . . . 813 



