LESSER BLACK- BACKED GULL. 67 



(1873); B. O. U. List Brit. B. p. 189 (1883); Saunders, 

 ed. Yarrell's Brit. B. iii. p. 624 (1884); Seebohm, Hist. 

 Brit. B. iii. p. 319 (1885) ; Saunders, Man. Brit. B. p. 659 

 (1889); Lilford, Col. Fig. Brit. B. part xxiii. (1893); 

 Saunders, Cat. B. Brit. Mus. xxv. p. 250 (1896). 



(Plate CI.) 



Adult Male. Similar to Z. marinus, but very much smaller, 

 and easily distinguished by the outer primaries, which have 

 not the ends white for nearly three inches, but are blackish 

 with a white sub terminal bar before a black tip. General 

 colour above slate-grey, with the same white ends to the 

 secondaries and scapulars ; the head, neck, mantle, and under 

 surface of body white, as also the rump, upper tail-coverts, 

 and tail ; " bill yellow, the angle of the genys red ; tarsi and 

 feet lemon-yellow ; iris pale straw-yellow " (Saunders). Total 

 length, 19-5 inches; culmen, 2-15; wing, 16-4; tail, 5-65 : 

 tarsus, 2 -6. 



Adult Female. Similar to the male, but smaller, and with a 

 less robust bill. Total length, 19*0 inches ; wing, i6'4. 



Adult in Winter. Differs from the summer plumage in having 

 the head and neck streaked with dusky-brown. 



Young. Brown above, with broad white margins, the head 

 brown, streaked with white; sides of face ashy brown, darker on 

 the ear-coverts, narrowly streaked with dusky ; throat white ; 

 remainder of the under surface of body streaked and mottled 

 with ashy-brown, which is the prevailing colour of the under 

 parts, the sides of the body barred with darker brown ; the 

 tail-feathers black for the terminal half, white barred with 

 black on the basal half, the black end decreasing towards the 

 outer feathers. The bill is slaty-grey, the feet flesh-coloured, 

 and the iris brown. It takes four years for the fully adult 

 plumage to be gained. 



Nestling. Greyish-buff, streaked and mottled with black on 

 the upper parts and throat. 



Characters. In examining the series of adult Lesser Black- 

 backed Gulls in the British Museum, one is struck by the 

 great variation in the colour of the back, from slaty-grey to 



F 2 



