
Photo: Alexis Lours · CC BY 4.0 (May be cropped or resized)
Chroicocephalus ridibundus
Habitat
Breeds in colonies in reed beds, marshes or on lake islands, nesting on the ground
Range
Breeds across the Palearctic; mostly migratory and winters further south
Size
34–39cm
Wingspan
100–110cm
Weight
166–400g
The black-headed gull is a small gull, 34 to 39cm long with a wingspan of 100 to 110cm, weighing 166 to 400g. The summer adult has a chocolate-brown head that looks black from a distance, a white neck, underparts and tail, pale grey wings and back, black primary tips, and a red bill and legs (Wikipedia, general species account).
It breeds across the Palearctic from Iceland and Ireland east to Japan and eastern China, in colonies of a few pairs up to several thousand. Most of the population is migratory and winters farther south. It is highly gregarious in winter, a bold and opportunistic feeder, and noisy, with a familiar 'kree-ar' call. The sources opened do not describe it in Bhutan.