BirdLife International

Distribution and population
The Black-tailed Gull is found in east Asia, specifically the coasts of eastern China, Japan, North Korea, South Korea and Sakhalin, Russia.

Population justification
The global population is estimated to number > c.1,100,000 individuals (Wetlands International 2006), while national population estimates include: c.100-100,000 breeding pairs and c.50-10,000 wintering individuals in China; c.50-1,000 wintering individuals, c.1,000-10,000 individuals on migration and < c.100 breeding pairs in Taiwan; c.10,000-100,000 breeding pairs in Korea; c.10,000-100,000 breeding pairs in Japan and c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Russia (Brazil 2009).

Trend justification
Although Wetlands International consider the current population trend to be unknown, it is suspected to be stable in the absence of evidence for any declines or substantial threats (del Hoyo et al. 1996).

Ecology
This species is found on coasts, and in bays and estuaries. Its diet varies locally and annually, but includes small fish, crustaceans, insects, offal, molluscs and polychaetes. It often follows fishing boats and can be a kleptoparasite. Colonies form mid-April on sandy or rocky seashores, sea cliffs and rocky islets. Many colonies hold over 10,000 pairs. Post-breeding it moves to areas rich in food (del Hoyo et al. 1996).