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, i6"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, 16*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 



