The smallest member of its family, the Red-throated Loon has a circumpolar distribution and breeds up to high latitudes. It is unique among loons in its appearance, plumage and molts, behavior, and vocalizations. Other loons undergo a delayed flight feather molt during mid- to late winter, but Red-throated Loons acquire new flight feathers just after fall migration. Other loons utter a yodel, an individually distinctive, male, territorial call, but Red-throated Loon pair members join in a territorial duet. Other loons need to run up to 100 m or more before taking flight from water; Red-throated Loons need less distance and can even launch from land.
In North America, the Red-throated Loon breeds mainly on remote ponds, primarily in coastal tundra habitat, so it is not often encountered by people. It is better known in Europe, where it breeds in more populated regions, including Scotland and Scandinavia. This is the only loon that regularly forages away from its nesting pond, flying to larger lakes or the sea not only to feed but also to carry single fish back to its young. Other loons rarely feed chicks from outside the nesting territory. In the most northern parts of its range, above 75°N, it has only 2-3 months to nest, hatch its eggs, and raise its young to fledging.
Numbers of this loon have declined recently in several parts of its range in North America, although it is not clear why. This species has been the subject of few recent studies in North America but considerable field research in Sweden and the United Kingdom. One of the earliest publications on avian behavior, and the first major work on any loon species, was J. S. Huxley's ( Huxley 1923 ) landmark treatise on Red-throated "Diver" behavior and the evolution of courtship in birds. In North America, locations of recent studies include the Queen Charlotte Islands (Douglas and Reimchen Douglas and Reimchen 1988a , Douglas and Reimchen 1988b ), the Beaufort Sea ( Dickson 1993 ), and the high Arctic ( Eberl 1993 , Eberl and Picman 1993 ). All these studies provide data on breeding biology and reproductive success.