434 LARIDAG 
black! The mature markings are gradually assumed, the 
mottled feathers first disappearing from the back and upper 
parts of the wings. A second year’s bird, showing the 
dark wings, and still retaining most of the chequered 
plumes of the under parts, appears on a dull, wintry day 
almost as dark as a Great Skua. The tail of the Lesser 
Black-backed Gull remains banded for several seasons, 
breaking up into mottlings before becoming pure white. 
The adult plumage is not completed until the fourth year. 
Beak. Yellow, red at the angle. 
Fret. Bright lemon-yellow. 
IrRIDES. Pale straw-colour. 
AVERAGE MEASUREMENTS. 
TOTAL LENGE ... ... 22 in. Female smaller. 
WING me nate ee Shon Lae 
BEAK A: D5 
TARSO-METATARSUS 2) MSO 
EGG 9:9 xs 1-Osaime 
Allied Species and Representative Forms.—L. affinis, 
larger, with a coarser foot, and with paler back and wings, 
called the Siberian River Gull, is the Eastern representative. 
L. occidentalis, with a very stout beak, and darker back and 
wings than in L. affinis, inhabits the Pacific Coast of North 
America. 
GREAT BLACK-BACKED GULL. Larus marinus (Linneeus). 
Coloured Figures.—Gould, ‘ Birds of Great Britain,’ vol. v, pl. 
55; Dresser, ‘ Birds of Europe,’ vol. viii, pl. 604 ; Lilford, 
‘Coloured Figures,’ vol. vi, pl. 25; Booth, ‘Rough Notes,’ 
vol. iii, pl. 37. 
This majestic bird, the largest of our indigenous Gulls, 
1 This distinction can only be arrived at when the two immature 
species are examined together in the hand. On the wing it is most 
difficult to discriminate between them after they have left their breeding- 
grounds and have taken to the coast. However, in August and early 
September, young Lesser Black-backed Gulls in dappled plumage may 
be seen following a parent, or, at all events, an adult of its own kind, 
and this is, I have found by experience, an opportune moment for 
securing a specimen of this bird. 
