American Herring Gull
Larus smithsonianus
The herring gull is a heavily built large gull with a long powerful bill, full chest and sloping forehead. Males are 60–66 cm (24–26 in) long and weigh 1,050–1,650 g (2.31–3.64 lb). Females are 53–62 cm (21–24 in) long and weigh 600–900 g (1.3–2.0 lb). The wingspan is 120 to 155 cm (47 to 61 in). Among standard measurements, the wing chord is 41.2 to 46.8 cm (16.2 to 18.4 in), the bill is 4.4 to 6.2 cm (1.7 to 2.4 in) and the tarsus is 5.5 to 7.6 cm (2.2 to 3.0 in). Breeding adults have a white head, rump, tail, and underparts and a pale gray back and upperwings. Voice: It has no song but possesses a variety of cries and calls. An initial call in response to a threat is a quick "hahaha", varying in intensity depending on the threat. The more-intense "keow" is a loud yet short alarm call that is both identifying and communicative of impending danger. The "long call" is a series of loud notes during which the head is dipped and then raised.
ID text from Wikipedia, CC BY-SA 4.0
Ring-billed Gull
Larus delawarensis
The ring-billed gull is a medium-sized gull, having an average length of 43 to 54 centimetres (16.9 to 21.3 in) and a wingspan that ranges from 105 to 117 centimetres (41.3 to 46.1 in). Adults weigh from 300 to 700 grams (10.6 to 24.7 oz). The head, neck and underparts are white; the relatively short bill is yellow with a black ring; the back and wings are silver grey with black wingtips with white 'mirrors'; and the legs are yellow. The eyes are yellow with red rims.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
And 8 more countries.
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: American Herring Gull and Ring-billed Gull.