Adult Plumage:
Summer Plumage: The head, neck, belly, and tail are white. The back and wings are ashy gray. The first primary feathers have gray bases. The second primary feathers have black tips with white spots. The third primary feathers have a black outer vane and tip with a relatively large white spot near the tip. In subsequent primary feathers, these white spots diminish in size, and the black at the feather tips also shrinks, disappearing entirely by the seventh primary feather. The secondary feathers and greater scapular feathers have white tips. The beak is yellow. The eyelids and eyes are red. The legs are pale green.
Winter Plumage: Similar to summer plumage, but with pale gray spots and streaks on the head.
Juvenile Plumage:
The back is pale brownish-gray with lighter feather edges. The underwing is black, with gray inner vanes. The uppertail coverts are white with horizontal barring. The tail feathers are white with black tips. The belly is white with pale rufous-gray streaks on the crop, breast, and flanks, or pale rufous-gray with lighter streaks. The beak is black with a pale yellow base. The legs are pale gray.
Measurements:
Wingspan (male): 331 – 410 mm
Wingspan (female): 328 – 395 mm
Distribution:
This gull species is distributed in eastern Northeast Asia; it migrates southward in winter.
Vietnam:
This species is very rare, having only been observed at a lake in Lạng Sơn.