GREAT BLACK-BACKED GULL 437 
stems, and seaweeds. The eggs, two sometimes three in 
number, are yellowish-brown or stone-colour, heavily 
blotched with umber and greyish-brown. 
Incubation begins in May. 
Around the sea-board of Northern Britain, including 
the large Island-Groups, the bird is fairly abundant in the 
nesting-season. Colonies of over twenty pairs breed in the 
Outer Hebrides. 
Likewise, round the greater part of the Irish coast it 
may be found breeding, except, perhaps, in the north-east. 
In the west it 1s more numerous than the Lesser Black- 
backed Gull. 
Along the English coast its breeding-haunts are much 
more restricted, the south and west sides, including Wales, 
harbouring only hmited numbers. 
Geographical distribution. — Abroad, this species 1s 
widely distributed over Northern and Temperate Europe, 
Greenland, and the North-eastern section of Canada. On 
migration, in autumn and winter, it occurs as far south as 
the shores of the Mediterranean and the Canary Islands on 
the North African coast. Westward, along the American 
sea-board, it reaches lat. 30° N. 
DESCRIPTIVE CHARACTERS. 
PLUMAGE. Adult male nuptial..—Head, neck, breast, 
abdomen, and tail, white; back and wings, slaty-black ; 
all the primaries, broadly tipped with white; outer 
primaries, chiefly blackish, except the tips; outer webs of 
other primaries chiefly blackish, inner webs, greyish ; 
secondaries and scapulars, also tipped with white forming 
an alar bar. 
Adult female nuptial.—Similar to the male plumage. 
Adult winter, male and female.—Differs from the nup- 
tial plumage in that the head and neck are streaked with 
greyish-brown. 
Immature, male and female. — Dappled with greyish- 
brown like the immature Herring-Gull, but the markings 
are paler and more defined. Seasonal plumage-changes, 
1 Thave seen this bird retain its nuptial plumage throughout the winter 
in a state of captivity. 
