Andean Gull
Chroicocephalus serranus
The Andean gull is 42 to 48 cm (17 to 19 in) long and weighs about 480 g (17 oz); it is one of the larger members of its genus. The sexes are alike. Adults in breeding plumage have a glossy black hood with a white crescent behind the eye and a mostly white body with a gray back and sometimes a pink flush on the underparts. Their tail is white. The upper side of their wing is mostly gray with an alternating white-black-white-black pattern on the primaries. The underside of their wing is pale gray with a blackish outer half but for large white "mirrors" on the three outermost primaries. Voice: The Andean gull's vocalizations include "agitated, sometimes tremulous "yeeer" calls" and "a hoarse "raggh-aggh-keeaagh" and other low raspy notes."
ID text from Wikipedia, CC BY-SA 4.0
Black-billed Gull
Chroicocephalus bulleri
A healthy adult black-billed gull is typically 35–38 cm long, with a wingspan of 81–96 cm, and a weight of around 230g. The head, body, and parts of the wings are white, with silvery grey on the saddle and wings, as well as black edging on the wings. The gull also undergoes some seasonal color change. While typically black from February to June, the orbital ring is orange-red, red, or dark red the rest of the year. The legs, too, change from black to dark red and even bright red as the breeding season progresses, "possibly stimulated by presence of begging chicks and juveniles.
ID text from Wikipedia, CC BY-SA 4.0
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Play today's Daily BirdPhotos and recordings are credited to their authors under the licence shown. Full profiles: Andean Gull and Black-billed Gull.