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
Common Loon
Gavia immer
The adult common loon can range from 66 to 91 cm (26 to 36 in) in length with a 127 to 147 cm (4 ft 2 in to 4 ft 10 in) wingspan, slightly smaller than the similar yellow-billed loon. On average, it is about 81 cm (32 in) long and has a wingspan of 136 cm (54 in). Its weight can vary anywhere from 2.2 to 7.6 kg (4.9 to 16.8 lb). Sizes vary regionally, especially by body mass, with the smallest bodied loons on average from lower-central Canada and the Great Lakes, while westerly birds are similar or mildly larger, and loons breeding further east can appear to be significantly larger. Voice: The common loon produces a variety of vocalizations, the most common of which are the tremolo, the yodel, the wail, and the hoot. Each of these calls communicates a distinct message. The frequency at which it vocalizes has been shown to vary based on time of day, weather, and season. It is most vocally active between mid-May and mid-June.
ID text from Wikipedia, CC BY-SA 4.0
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