Common Loon

Common Loon
Photo by Gary J. Wege/USFWS Midwest Region.

"The woodland lakes would be solitudes, indeed, did they lack the finishing touch to make the picture complete – the weird and mournful cry of the loon, as he calls to his mate or greets some new arrival. Who has ever paddled a canoe, or cast a fly, or pitched a tent in the north woods and has not stopped to listen to this wail of the wilderness? And what would the wilderness be without it?"
~ Arthur Cleveland Bent, ornithologist

A common loon in summer is an eye-catching sight, with bright red eyes, a black-and-white checkered back, iridescent dark-green head, and prominent white necklace. During the winter, they molt into plainer gray and white plumage. Males and females look alike, although male loons are usually about 25 percent larger. Young common loons look similar to winter adults, but have more white on their head and back. This juvenile plumage is maintained through their first summer. Common loons are large swimming birds with long bodies that sit low in the water. They average 2.5 feet in length with a 5-foot wingspan and have dagger-like bills that are black in the breeding season and gray during the rest of the year. Loons are well equipped for submarine maneuvers. Unlike most birds, loons have solid bones that make them less buoyant and better at diving. They can quickly flatten their feathers to expel air within their plumage, so they can dive quickly and swim fast underwater. Once below the surface, the loon’s heart slows down to conserve oxygen. Their legs are set far back on their bodies, which also helps them maneuver through water, but causes them to move awkwardly on land. They spend little time on land though, typically only going ashore to nest. Many people consider the loon a symbol of wilderness; its rich yodeling and moaning calls, heard by day or night, are iconic sounds of early summer in the north woods. In winter, common loons inhabit coastal waters and large southern lakes. Their genus, Gavia, is derived from the Latin term for an unidentified seabird and their species, immer, is derived from a Norwegian name for the bird, similar to the modern Icelandic word "himbrimi.” The word may be related to to Swedish immer and emmer, the grey or blackened ashes of a fire (referring to the loon's dark plumage); or to the Latin immergo, to immerse.

This species is most abundant in Canada and the Northern United States. Common loons breed on lakes and other waterways from western Greenland west across Canada and the northernmost United States, including Alaska. However, they winter as far south as Baja California and Texas.

Loons are visual predators, locating fish by sight and diving to catch them. They generally hunt in water 6 to 13 feet deep. Since they hunt by sight, loons require clean, clear water to successfully locate prey. Adult loons ingest most of their food items underwater where they catch them, but will bring larger items to the surface to eat. They can stay submerged for up to 5 minutes. The loon has sharp, rearward-pointing projections on the roof of its mouth and tongue that help it keep a firm hold on slippery fish. Before diving, they may swim on the surface with their head partly submerged to peer underwater. Loons do all their feeding during the day, when they can best see their prey. They eat fish and other aquatic animals, including crayfish, shrimp, leeches, frogs, mollusks, aquatic insects, and some aquatic vegetation. A hungry loon family can put away a lot of fish. It has been estimated that a family of loons (2 parents and 2 chicks) can eat over 60 pounds of fish per week.

Loons are agile swimmers, but they move pretty fast in the air, too. Migrating loons have been clocked flying at speeds more than 70 mph. Their legs are placed far back on their bodies, making them very powerful underwater swimmers. However, this arrangement also makes walking difficult for these birds. Because of this and their relatively heavy bodies, they require a long "runway" to take off for flight and can only do so from water. They need from 30 yards up to a quarter-mile (depending on the wind) for flapping their wings and running across the top of the water in order to gain enough speed for lift-off. Their legs trail out behind them while in flight, a characteristic shared by all loon species. When landing, loons make an inelegant belly flop, then skim along the water on their bellies to slow down. Migrating loons sometimes get into trouble when they mistake icy roads, parking lots, or other solid surfaces for water and can't take off again after landing. A loon may also get stranded on a pond that is too small. They are also flightless for a few weeks after molting all of their wing feathers simultaneously in midwinter.

Common loons have a number of distinctive calls. One of the most well-known is a tremulous call used when they feel threatened, particularly in the vicinity of their nests. Another well-known call is the eerie, double-noted wail, which seems to function as a contact and gathering call. A third vocalization, the yodel, is given only by the male during territorial defense. Each male has his own characteristic yodel, but surprisingly, when a male loon changes territory, he changes his yodel. A fourth call, the hoot, is a one-note vocalization used by family members to locate each other. They are often very vocally active with nocturnal choruses. After sundown, many lakes in their northern range reverberate with the echoes of loon wails, yodels, and tremolos – which writer John McPhee called “the laugh of the deeply insane,” and may have given the bird it’s common North American name.

Loons are not typically social birds. You can usually find them foraging by themselves during the day. Though at night, they sometimes form loose flocks while they sleep. Even when they migrate, they typically, though not always, fly alone.

Common loons breed once per year in the spring and summer on lakes surrounded by forests in Canada and the Northern US. They are monogamous, with pair bonds lasting for multiple years. A breeding pair usually defends a territory consisting of an entire small lake or a protected bay within a large lake. They establish a territory of 60 to 200 acres, which they patrol regularly. Pairs exhibit high site fidelity and will reuse a nest site from the previous year if they successfully hatched chicks there. In spring, loon mates arrive back on their lake separately. If one year one of the mates doesn’t return, the other will quickly pair up with another mate. The male defines his territory through yodeling. Courtship consists of swimming in circles, synchronous dives, and racing side by side across surface of water.

Both members of a pair build a large, mounded nest of dead marsh grasses, twigs, reeds, and other plants approximately 2 feet in diameter. The nest can be built either on the ground or afloat in shallow water, ideally near deep water so they can swim to and from the nest without being seen by predators. They favor nest sites on small islands or peninsulas but will also build along well-vegetated shorelines. When the nest is complete, the female lays 1 to 3 brown spotted eggs, one or two days apart. Male and female take turns incubating their eggs and protecting the nest, beginning after the first egg has been laid. Incubation lasts for around 29 days. The chicks hatch asynchronously, up to a day apart. They stay in the nest for a day or two after hatching, after which time they leave the nest with the parents and return to shore only rarely. The dark, downy chicks can swim and dive after only two to three days and have an endearing habit of riding on their parents' backs, usually for the first seven to ten days after hatching. The parents feed the chicks whole food every hour from the time of hatching until they are up to three months old. They protect the chicks from predators by vocalizing and swimming away to distract them from the chicks. When that doesn’t work, loons sometimes attack the predator by rushing at it and attempting to impale it through the abdomen or the back of the head or neck. Chicks remain with their parents for up to three months, until they are able to fly. The parents head off on migration in the fall, leaving juveniles to gather into flocks on northern lakes and make their own journey south a few weeks later. Once the juveniles reach coastal waters on the ocean, they stay there for the next two to three years before heading back north to breed. The oldest recorded common loon was a female, and at least 29 years and 10 months old when she was spotted in Michigan in 2016 and identified by her band. She was originally banded in the same state in 1989.

Common loons are predators, so they accumulate toxins, such as mercury or heavy metals, that are concentrated by every rung up the food chain. Lead poisoning through ingestion of fishing sinkers, which loons mistake for grit, is another major cause of mortality, and these birds face additional dangers from oil spills, fishing nets, habitat loss, and climate change.

North American common loon populations are stable overall. They depend on clean water and are sensitive to the effects of pollution and human disturbances. They have special conservation status in some states where they are listed as threatened, though the IUCN Red List classifies them as Least Concern. They are also protected by the U.S. Migratory Bird Act.

Where I learned about loons, and you can too!

Michigan State University

Animal Diversity Web

IUCN Red List

US Fish & Wildlife Service


Cornell Lab of Ornithology

The National Wildlife Federation

American Bird Conservancy