47. Larus marinus 
GREAT BLACK=-BACKED GULL. 29 inches 
Adult. In summer. Above, head white; back and upper sur- 
face of wings blackish; long quill feathers black tipped with 
white; tail white. Below, white; bill yellow; feet pink. In win- 
ter. Similar but head streaked with brown. Immature. White, 
thickly mottled with brown, darker on the back and wings. The 
largest and handsomest of the common gulls. 
Note. ‘A harsh, whistling fevw.” 
Breeds. North of New England. A rather common winter vis- 
itor along the coast and in the harbors from September to April. 
17 
