Sabine's Gull
Xema sabini
Sabine's gull is a small gull, 27 to 33 cm (10+1⁄2–13 in) in length and weighing 135 to 225 g (4+3⁄4–8 oz). The wings are long, thin and pointed with a span of between 81 and 87 cm (32–34+1⁄2 in). The bill, which is black with a yellow tip, is around 2.5 cm (1 in) long. This species is easy to identify through its striking wing pattern, though at long range it can be confused with immature black-legged kittiwakes. The adult has a pale grey back and wing coverts, four black outer primary flight feathers, and white inner primaries and secondaries. The white tail is slightly forked.
ID text from Wikipedia, CC BY-SA 4.0
Slender-billed Gull
Chroicocephalus genei
This species is 37 to 40 cm (14.6 to 15.7 in) long with a 90 to 102 cm (35.4 to 40.2 in) wingspan. It is therefore slightly larger than the black-headed gull, which it resembles, although it does not have a black hood in summer. It has a pale grey body, white head and breast and black tips to the primary wing feathers. The head and dark red bill have an elongated tapering appearance, and this bird also appears long-necked. The legs are dark red, and the iris is yellow. In summer, the breast has a faint pink colouration. This bird takes two years to reach maturity, as is usual in gulls.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
Learn this pair in BeakBrain
Photo and call practice, free in any browser.
Play BeakBrainPhotos and recordings are credited to their authors under the licence shown. Full profiles: Sabine's Gull and Slender-billed Gull.