Black Guillemot
Cepphus grylle
The black guillemot is a medium-sized bird with adults normally 30 to 32 centimetres (12 to 12+1⁄2 inches) in length and with wingspans of 52 to 58 cm (20+1⁄2 to 23 in). The bodyweight can range from 300 to 460 grams (10+1⁄2 to 16 ounces). Adults have both summer and winter plumage and there is no sexual difference in this that can be identified in the field. The English common name "Black Guillemot" references their strikingly black breeding summer plumage which is totally black except for a large white patch on the upper side of their wings.
ID text from Wikipedia, CC BY-SA 4.0
Pigeon Guillemot
Cepphus columba
The pigeon guillemot is a medium-sized auk, 30 to 37 cm (12 to 15 in) in length and weighing 450 to 550 g (16 to 19 oz). Both sexes are alike in appearance and mass, except for Californian birds where females were found to have larger bills than males. The summer or breeding plumage of the adult is mostly dark brown with a black sheen, with a white wing patch broken by a brown-black wedge. In winter, the upperparts are iridescent black, often with black fringes giving a scalloped appearance, and the underparts and rump are white.
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: Black Guillemot and Pigeon Guillemot.