Adult Plumage:
Summer plumage: Resembles the species in general but exhibits a paler brown coloration on the head. The lower edge of this brown area forms a darker band above the nape. Primary feathers 1 and 2 are black with small white spots at the base and a larger white spot at the tip. The third primary is black with a white bar. The last primary is gray with a black tip. Eyes are reddish-brown or yellowish-brown. The beak, eyelids, bill edges, and legs are red.
Winter plumage: The brown coloration on the head disappears.
Juvenile Plumage:
Resembles the juvenile plumage of Larus ridibundus (Black-headed Gull), but the primary feathers are blackish-brown. The bare skin around the eyes, beak, and legs is yellow or orange.
Measurements:
- Wing: 330 – 340 mm
- Tail: 139 – 159 mm
- Tarsus: 49 – 55 mm
- Bill: 37 – 45 mm
Distribution:
This species breeds in eastern Tibet and migrates south during the winter. In Vietnam, it is frequently observed, particularly in the coastal estuaries and large rivers of the South.