BLACK-HEADED GULL 411 
Both sexes take part in the task of incubation. 
Geographical distribution.—The breeding-grounds extend 
over a wide area of Sub-arctic and Temperate Kurope east 
of the Baltic ; eastward this bird breeds in Temperate Asia. 
In winter it miorates to the Mediterranean Basin and to 
North Africa as far as Egypt. 
DESCRIPTIVE CHARACTERS. 
PLUMAGE. Adult male nuptial.—Head and upper neck, 
black ; rest of neck, white; back and wings, ‘ french’ grey ; 
primaries, grey, broadly edged with white, darker on their 
inner webs; axillaries and under wing-coverts, blackish, con- 
spicuous when the bird is flying; tail, white; throat, breast, 
and abdomen, white, exhibiting a delicate pinkish hue. 
Adult female nuptial.—Similar in pluinage to the male. 
Adult winter, male and female.—Forehead, white ; top 
of head, back of neck, and cheeks, greyish. 
Immature, male and female—Vop of head and back of 
neck, streaked with brownish-grey ; back and wings, mottled 
with dark brown, and edged with buff; tail, banded sub- 
terminally with a similar colour; primaries, black, edged 
internally with white; under wing-coverts and axillaries, 
white. 
Beak. Lake-red. 
FreEr. Vermilion-red. 
Ir1DES. Brownish-black. 
AVERAGE MEASUREMENTS. 
TOTAL LENGTH ... =: shag! ca in. 
WING ‘ a ae Bae Srione 
Brak ee ea Fe bree 
TARSO-METATARSUS 1 : 
Kae 165; semaleaa 
BLACK-HEADED GULL. Larus ridibundus (Linneus). 
Colowred Figures.—Gould, ‘ Birds of Great Britain,’ vol. v, pl. 
64; Dresser, ‘Birds of Europe,’ vol. viii, pls. 596, 597, 
fig. ate imilroad: ‘Coloured Figures,’ vol. vi, pl. 19; Booth, 
‘Rough Notes,’ vol. iii, pls. 35, 36. 
This familiar species is widely distributed, not only 
along the sea-coast of the British Isles, but also, during 
the breeding-season, in marshy situations, often miles away 
