The black-throated loon, also known as the Arctic loon and the black-throated diver, is a migratory aquatic bird found in the northern hemisphere, primarily breeding in freshwater lakes in northern Europe and Asia. It winters along sheltered, ice-free coasts of the north-east Atlantic Ocean and the eastern and western Pacific Ocean. This loon was first described by Carl Linnaeus in 1758 and has two subspecies. It was previously considered to be the same species as the Pacific loon, of which it is traditionally considered to be a sister species, although this is debated. In a study that used mitochondrial and nuclear intron DNA, the black-throated loon was found to be sister to a clade consisting of the Pacific loon and two sister species, the common loon and the yellow-billed loon.
Region
Northern Eurasia
Typical Environment
Breeds on clear, oligotrophic to mesotrophic freshwater lakes and large ponds across the boreal and subarctic zones of northern Europe and Asia. Prefers lakes with islands or sheltered shorelines and ample open water for takeoff and landing. During migration it uses large lakes, reservoirs, and rivers as stopover sites. In winter it favors sheltered, ice-free marine coasts, bays, and estuaries along the North Atlantic and North Pacific.
Altitude Range
Sea level to 1500 m
Climate Zone
Polar
Ease of Keeping
Beginner friendly: 1/5
A superb underwater pursuit diver, the black-throated loon can stay submerged for over a minute while chasing fish. Adults often carry small chicks on their backs to keep them warm and safe from predators. It requires a long water “runway” to take off, which makes it vulnerable to disturbance on small lakes. It was long confused with the Pacific loon but is now treated as a separate species.
Breeding, top, and non-breeding, bottom, black-throated loons
Non-breeding adult
A black-throated loon taking off
Black-throated loon family feeding on Lake Stråken, Sweden
Eggs, Collection Museum Wiesbaden, Germany
Temperament
solitary and territorial
Flight Pattern
strong flier; low over water with rapid, shallow wingbeats; requires a long running takeoff
Social Behavior
Typically breeds in isolated pairs that defend territories on suitable lakes. Nests are placed at the water’s edge or on small islets; both adults incubate 1–2 eggs and care for the young. Parents often transport chicks on their backs during the first weeks after hatching. Outside the breeding season, small groups may form on migration and wintering coasts.
Migratory Pattern
Seasonal migrant
Song Description
Gives haunting, far-carrying wails and moans across breeding lakes, especially at dusk and night. Also produces harsher croaks and tremulous calls during territorial encounters and pair communication.
