540 ORNITHOLOGY AND OOLOGY. 



young, which they eat. They are, in the water, almost pre- 

 cisely what the Crows and Jays are on the land. 



LABUS MABINUS. Linnceus. 

 The Great Black-backed Gall. 



Larva marinua, Linnaeus. Syst. Nat, I. (1766) 225. Nutt. Man., n. (1834) 308. 

 Aud. Birds Am., VII. (1844) 172. 



DESCRIPTION. 



Adult. The head, neck, entire under plumage, upper tail coverts, and tail 

 are pure-white; the back and wings are of a dark-slate color; the primaries are deep 

 black, largely tipped with white, as are the extremities of most of the quills ; the 

 bill is gamboge-yellow, with an orange-red spot near the end of the lower mandible ; 

 legs and feet pale-yellow; iris white. 



Young. Head, rump, and under plumage grayish-white, with streaks of light- 

 brown ; back and wings mottled with brownish-ash and grayish-white ; primaries 

 blackish-brown, having the tips edged with white; tail white, spotted with brown, 

 and having a broad subterminal band of the same color; bill brownish-black, yel- 

 lowish at the base ; legs and feet yellow. 



Length, about thirty inches ; wing, twenty; tail, nine; bill, two and ten -twelfths ; 

 tarsus, two-twelfths of an inch. 



Hob. North Atlantic, Labrador; as far south as Florida in winter. 



The Black-backed Gull is of frequent occurrence on our 

 coast in the autumn and winter months ; and, according to 

 Mr. George A. Boardman, a few breed as far south as the 

 islands in the Bay of Pundy. Audubon describes its 

 breeding habits as follows : 



" The nest of this species is usually placed on the bare rock of 

 some low island, sometimes beneath a projecting shelf, sometimes 

 in a wide fissure. In Labrador, it is formed of moss and seaweeds 

 carefully arranged, and has a diameter of about two feet ; being 

 raised on the edges to the height of five or six inches, but seldom 

 more than two inches thick in the centre, where feathers, dry grass, 

 and other materials, are added. The eggs are three, and hi no 

 instance have I found more. They are two inches and seven- 

 eighths in length by two inches and one-eighth in breadth ; broadly 

 ovate ; rough, but not granulated ; of a pale earthy greenish-gray 

 color, irregularly blotched and spotted with brownish-black, dark- 

 nmber, and dull-purple." 



