Common Loon

What Is a Common Loon?

The common loon (Gavia immer) is a large, striking waterbird known for its haunting, far-carrying calls that echo across northern lakes on summer evenings. It is one of five loon species worldwide and belongs to an ancient lineage of foot-propelled diving birds superbly adapted to life on the water.

Appearance and Identification

In breeding plumage, the common loon is unmistakable: a glossy black head with a greenish sheen, a bold necklace-like band of white streaks around the throat, a checkerboard pattern of white spots across a black back, and a clean white breast. The bill is stout, dagger-shaped, and held level. Adults have deep red eyes. In winter, the plumage fades to a plainer gray-brown above and white below. Males and females look alike, though males tend to be somewhat larger. Adults typically measure 26 to 36 inches long with a wingspan of roughly four to five feet, and weigh between about 5 and 13 pounds depending on sex, season, and region.

Habitat and Range

Common loons breed across the northern United States, Canada, Alaska, Greenland, and Iceland, favoring clear, deep freshwater lakes with plenty of small fish and quiet shorelines for nesting. Clear water matters because loons hunt by sight underwater. In fall they migrate to milder waters, wintering along the Atlantic and Pacific coasts, in the Gulf of Mexico, and on some large ice-free inland lakes and reservoirs. During the nonbreeding season they generally live on saltwater or coastal bays.

Diet

The common loon is a carnivore that feeds mainly on fish, which it pursues in underwater chases. It also takes crayfish, aquatic insects, mollusks, leeches, and occasionally amphibians. Loons are powerful divers, propelling themselves with large, rearward-set webbed feet, and can remain submerged for a minute or more while foraging. They usually swallow small prey underwater and bring larger catches to the surface.

Behavior

Loons are highly aquatic and awkward on land, because their legs sit far back on the body, an arrangement that makes them exceptional swimmers but poor walkers. Their bones are denser than those of most birds, reducing buoyancy and aiding their deep dives. To become airborne they need a long running takeoff across open water. Common loons are famous for four main vocalizations: the wail, the tremolo, the yodel (given by males), and the hoot. These calls carry over long distances and are used to defend territory, keep pairs and families in contact, and signal alarm.

Life Cycle and Reproduction

Common loons form seasonal pair bonds and defend breeding territories on their lakes. The nest is a simple mound of vegetation built at the water’s edge or on a small island, where the birds can slip on and off easily. Females typically lay one or two olive-brown, spotted eggs, and both parents share incubation for roughly four weeks. The downy chicks leave the nest within a day or so and often ride on their parents’ backs for warmth and protection from predators. Young loons are fed and guarded for several weeks before becoming independent. They reach breeding age after a few years and may live 15 to 30 years in the wild.

Conservation Status

The common loon is listed as Least Concern by the IUCN, with a large range and a stable overall population. Even so, it faces regional threats, including lakeshore development, human disturbance during nesting, entanglement in fishing gear, and poisoning from ingesting lead fishing sinkers. Mercury and other pollutants that accumulate in fish can also harm loons and lower breeding success. Acid rain and declining water clarity affect prey availability on some lakes. Conservation efforts include protecting nesting habitat, promoting nontoxic fishing tackle, and monitoring populations.

Frequently Asked Questions

Why do loons have such eerie calls? Their wails, tremolos, and yodels help pairs and families stay in contact across a lake, defend territory, and warn of danger. Sound carries well over water, so the calls travel long distances.

Can loons walk on land? Barely. Their legs are set far back for powerful swimming and diving, which makes them clumsy on land. They come ashore mainly to nest and otherwise stay on the water.

How deep can a common loon dive? Loons commonly dive to depths of a few dozen feet in pursuit of fish and can stay underwater for a minute or more, using their strong webbed feet for propulsion.