The black-tailed gull (Larus crassirostris ) is a gull native to shorelines of East Asia.
The black-tailed gull is medium-sized (46 cm) (19 Inches), with a wingspan of 126–128 cm (49.6 - 50.3 Inches). It has yellow legs and a red and black spot at the end of the bill. Males and females have identical plumage and features, although males are larger in size than females. This gull takes four years to reach full adult plumage. As the name suggests, it has a black tail. The bird has a cat-like call, giving it its Japanese name — umineko (海猫, "sea cat"), and Korean name — gwaeng-yi gull, which means "cat" gull. In Hachinohe they are one of the 100 Soundscapes of Japan.
The species is resident to coastlines of the East China Sea, Japan, Manchuria and the Kuril Islands. It is a vagrant to Alaska and North America and has been found in the Philippines.
The black-tailed gull feeds mainly on small fish, molluscs, crustaceans scraps and carrion. A study analyzing the identifiable parts of gull excreta in Korea found that 19.1% consisted of the remains of fish, 3.3% of crustaceans, and 3.3% of land insects.
The species often follows ships and commercial fishing fleets. It also steals food from other seabirds. It is a colonial nester, with colonies forming in mid-April. 2–3 eggs are laid by early June. Incubation lasts approximately 24 days.
Black-tailed gulls use a variety of voice signals and are known to use more than 10 different sounds for communication. Young can recognize their parents from their voice and visual stimulation between 10 and 15 days after hatching, and can also distinguish between siblings and non-siblings. Alarm calls are alert signals that warn of predators or danger. Aggressive calls accompany attacks on predators. Contact calls are signals used for intra-specific communication. The most commonly heard cat-like sound ("mew call") is a part of the contact call, and is frequently used, such as when returning to the nest after taking food, alternating the role of the mating and nesting, taking care of the young, collective flight, etc. The sound of a young gull begging for food and the sound of a female during mating are also included in the contact call.
