Common loon (Gavia immer)

Physical description

Common loons typically measure 26 to 36 inches, with a 50 to 55-inch wingspan. They weigh 8.4 to 19 pounds. Loons have powerful legs set far back on their body, making them highly adapted for swimming and diving, but incapable of walking on land. Males are larger than females and territorial individuals tend to be larger than those not on territories. Both male and female common loons bear black and white plumage during the breeding season. Full alternate (breeding) plumage is not attained until 36 months of age. Subadult loons may remain in basic plumage year-round. In winter, loons acquire gray plumage above and are white below. 

Learn about and listen to different loon calls.

Ecology and life history

In winter, the majority of common loons reside in marine and estuarine coastal waters. Larger inland lakes, reservoirs and rivers are used during migration and also in winter. 

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Photo by U.S. Fish and Wildlife Service - Umbagog Wildlife Refuge

Common loons feed mainly on fish, typically of a size between 0.35 to 2.45 ounces. In fresh water, these include shad, alewife, trout, smelt, mudminnows, dace, chubs, shiners, suckers, sticklebacks, bluegills, crappie, yellow perch, and walleye. Saltwater prey include eels, menhaden, herring, haddock, whiting, pipefish, shiner perch, sandlance, gobies, blennies, Irish lords, gurnards, sculpins, flounder, sole, and skates. They also occasionally take amphibians, crayfish, small crabs, and dragonflies; and in eastern Washington, adults have been observed feeding dragonfly nymphs to their chicks.

North American banding studies show that common loons do not begin breeding until at least 6 years of age. Since loons cannot walk on land, they require nesting sites at the very edge of deeper waters, in marshy portions of lakes in water depths typically around 2 to 3 feet. Breeding habitat requires usually clear lakes containing both shallow and deep-water areas, or aquatic vegetation mats extended out from shorelines over deeper water. Nest sites include hummocks of reeds/cattails separated from the mainland, small islands, and floating logs that have thick vegetation side cover (tall grass, cattail, small shrub). Optimal nests sites include overhead cover to conceal eggs from predators, protection from wind and waves, allow good visibility for incubating adults, and a steep underwater slope adjacent to the nest for adequate underwater approaches and exits.

Egg-laying in Washington generally begins between mid-May and mid-June. The earliest known consistent egg laying date is end of April from one pair in western Washington. Incubation is usually 25 to 32 days. Chicks leave the nest within 24 hours of hatching and are soon moved to nursery areas for rearing, which are typically located in shallow coves of fairly uniform depth, sheltered from prevailing winds and wave action, and may be independent of the nest site location. Chicks up to three weeks of age may be carried on their parents' backs. Most juveniles are capable of flight at 11 to 12 weeks, and some leave their small, natal lakes or parental territories shortly afterward.

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Photo by National Park Service- Acadia National Park

Successful parents usually remain bonded and have high site fidelity, meaning the pair return to the same nesting territories in successive years.

Non-breeding loons (single non-territorial “floaters”) tend to aggregate during summer in nearshore marine waters, but also will also spend summers inland at unoccupied lakes and freshwater bodies. Life span is estimated to about 30 years. The oldest known loon in Washington is 25 years.

Adult loons are considered an apex species, and so predation of adults on their breeding lakes is considered rare, but there is documentation of a bald eagles in Washington predating on a breeding adult loon on its territory. As bald eagles have increased in numbers, loon chicks and eggs have been increasingly prone to eagle predation; eagles are likely the largest cause of chick mortality in recent years. Other lesser predators are mink and raccoon.

Geographic range

Common loons breed in freshwater habitats of northern North America including much of Canada, Alaska, northern portions of the contiguous United States, and southern Greenland. They also breed in Iceland. The southern portion of their historical breeding range has contracted. Western North American residents spend winters on inland larger freshwater bodies and marine environments from Alaska to northern Mexico.

Common loons were once described as a fairly common breeding species both east and west of the Cascade crest, but likely declined between 1890 and 1925 in much of Washington. Declines across the United States during this period are thought to have been the result of hunting, shoreline development and habitat alteration at nesting lakes.

In Washington, breeding areas are freshwater lakes and reservoirs, mainly in remote areas in the northern tier of the state. Common loons spend the winter in almost all nearshore marine habitat and larger freshwater bodies of western Washington. They are uncommon and irregular in winter in eastern Washington where they are found in large water bodies and Columbia Basin impoundments. The size of Washington’s breeding population is small, currently known at around 23 pairs and estimated in total at less than 50 pairs.

For a map reflecting this species' conservation status and other species' information, check out NatureServe Explorer and the International Union for Conservation of Nature Redlist.