LOON

Common loon, or great northern diver (Gavia immer) also called Diver (Gavia), any of four species of diving birds constituting the family Gaviidae (order Gaviiformes). These birds were formerly included, along with the grebes, to which they bear a superficial resemblance, in the order Colymbiformes (q.v.). Loons range in length from 60 to 90 cm (2 to 3 feet). Characteristics include a strong, tapered bill; small pointed wings; webs between the front three toes; and legs placed far back on the body, making walking awkward. Loons have thick plumage, mainly black or gray above and white below. During the breeding season the dorsal plumage is patterned with white markings, except in the red-throated loon (species Gavia stellata), which, during the summer, is distinguished by a reddish brown throat patch. In winter the red-throated loon develops white speckling on the back, while the other species lose these markings. Almost wholly aquatic, loons can swim long distances underwater and can dive from the surface to a depth of 60 m (200 feet). They are generally found singly or in pairs, but some species, especially the Arctic loon, or black-throated diver (G. arctica), winter or migrate in flocks. The voice is distinctive, including guttural sounds and the eerie, wailing cries, which in North America gave rise to the common name loon. They feed mainly on fishes, crustaceans, and insects. The nest is usually a heap of vegetation at the water's edge, in which two (or rarely three) olive-brown, spotted eggs are laid. The parents share the task of incubation. The chicks hatch in about 30 days and, as soon as their down is dry, enter the water with the parents. Although loons are strong fliers, all but the small red-throated loon need a broad expanse of water for takeoff. Thus, except for G. stellata, they are limited to large lakes. The common loon, or great northern diver (G. immer), is the most abundant loon in North America; its counterpart across Eurasia is the similar white- (or yellow-) billed diver (G. adamsii). The red-throated and arctic loons are virtually circumpolar in distribution, the latter being most abundant on the Pacific coast of North America.