Black-tailed Gull vs Slaty-backed Gull

Black-tailed Gull

Larus crassirostris

Large561 gCoastal

The black-tailed gull is medium-sized (46 cm or 18.1 in), with a wingspan of 126–128 cm (49.6–50.4 in). 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 their calls are one of the 100 Soundscapes of Japan.

ID text from Wikipedia, CC BY-SA 4.0

Photo: Angie from Sawara, Chiba-ken, Japan · CC BY 2.0

Slaty-backed Gull

Larus schistisagus

Large1.3 kgCoastal

It is tied with the yellow-footed gull for fourth-largest gull species, measuring 55–68.5 cm (21.7–27.0 in) in length, 132–160 cm (52–63 in) in wingspan, and 1.05–1.7 kg (2.3–3.7 lb) in weight. Among standard measurements, the wing chord is 40 to 48 cm (16 to 19 in), the bill is 4.8 to 6.5 cm (1.9 to 2.6 in), and the tarsus is 6 to 7.6 cm (2.4 to 3.0 in). It has a white head, belly, and tail with a dark slaty-gray back and wings with a broad white trailing edge. The wings and back are slightly darker than those of the western gull (Kodak grey scale 9.

ID text from Wikipedia, CC BY-SA 4.0

Photo: Original: ほくなん. This edit: MPF · Public domain

Photos and recordings are credited to their authors under the licence shown. Full profiles: Black-tailed Gull and Slaty-backed Gull.