Ivory gull narrower os pubis, and potentially more flexibility in skull kinetic structure. Structurally, it is most similar to the kittiwakes; however, recent genetic analysis based on mtDNA sequences shows that Sabine's gull is the ivory gull's closest relative, followed by the kittiwakes, with Ross's gull and swallow-tailed gull sharing a clade with these species. "Pagophila" is maintained as a unique genus because of the bird’s morphological, behavioral and ecological differences from these species. Colloquial names from Newfoundland include slob gull (from "slob", a local name for drift ice) and ice partridge, from a vague resemblance to a ptarmigan. This species is
Black-tailed gull "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 bird is common in Japan, nesting from Hokkaido to Western Kyushu. It has caused flights to be delayed at Haneda Airport in Tokyo. An enormous gathering of black-tailed gulls can be found at the Kabushima at Hachinohe, Aomori, Japan. A Shinto shrine was raised by fishermen in 1269 (though