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
Great Black-backed Gull
Larus marinus
This is the largest gull in the world, considerably larger than a herring gull (Larus argentatus); only two other gulls, glaucous gull (Larus hyperboreus) and Pallas's gull (Ichthyaetus ichthyaetus), come close to matching this species in size. It is 64–79 cm (25–31 in) long with a 1.5–1.7 m (4 ft 11 in – 5 ft 7 in) wingspan and a body weight of 0.75–2.3 kg (1 lb 10 oz – 5 lb 1 oz). In a sample of 2009 adults from the North Atlantic, males were on average 1,830 g (4 lb 1⁄2 oz) and females were on average 1,488 g (3 lb 4+1⁄2 oz).
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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Play today's Daily BirdPhotos and recordings are credited to their authors under the licence shown. Full profiles: American Herring Gull and Great Black-backed Gull.