Black-throated Loon
Gavia arctica
The adult black-throated loon is 58 to 73 cm (23 to 29 in) in length with a 100 to 130 cm (39 to 51 in) wingspan and a weight of 1.3 to 3.4 kilograms (2.9 to 7.5 lb). The nominate subspecies in its breeding plumage has a grey head and hindneck, with a black throat and a large black patch on the foreneck, both of which have a soft purple gloss. The lower throat has a necklace-shaped patch of short parallel white lines. Voice: The male, when breeding, vocalizes a loud and rhythmic "oooéé-cu-cloooéé-cu-cloooéé-cu-cluuéé" whistling song. A "áááh-oo" wail can also be heard, and a growling or croaking "knarr-knor", a sound given especially at night. The alarm call at the nest is a rising "uweek".
ID text from Wikipedia, CC BY-SA 4.0
Yellow-billed Loon
Gavia adamsii
With a length of 76 to 97 cm (30 to 38 in), a wingspan of 135 to 160 cm (53 to 63 in), and a weight ranging from 4 to 6.4 kg (8.8 to 14.1 lb), the yellow-billed loon is the largest member of the loon (diver) family. The adult is primarily black and white in breeding plumage, with a purple gloss on its head and neck. Appleby, R.H.; Madge, S.C.; Mullarney, Killian (1986). "Identification of divers in immature and winter plumages". British Birds. 79 (8): 365–391.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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