Common Loon (Gavia immer): Facts, Calls, Diving and Habitat

Appearance: how to recognize a common loon

In summer the common loon is one of the most striking birds of the North. The head and neck are black with a green or purple gloss, set off by a white striped “necklace” and collar. The back is black with a checkerboard of white squares, the underparts are pure white, and the eyes are deep red. The heavy, dagger-shaped bill is black.

In winter loons look very different: gray-brown above and white below, with a pale throat, a grayer bill and none of the bold pattern. Males and females look alike, though males are larger and heavier. Young birds resemble winter adults, with scaly-looking backs.

Loons sit very low in the water, sometimes with only the head and neck above the surface. In flight they look hunchbacked, with the head held slightly low and the big feet trailing behind the tail.

Size: how big is a common loon?

The common loon is a big, heavy bird, about the size of a large duck or a small goose.

Size varies by region: loons breeding in northeastern North America tend to be heavier than those around the Great Lakes. In some populations males are up to about a quarter heavier than females. Only the closely related yellow-billed loon of the Arctic is larger.

Habitat and range

Common loons breed across Alaska, Canada and the northern United States, from Maine and New York west to Minnesota, Wisconsin, Michigan, Montana and Washington. They also breed in Greenland and Iceland, and in very small numbers in Svalbard. In summer they need clear lakes big enough for take-off, with plenty of small fish and quiet shorelines or islands for nesting.

In autumn they move to coasts and large ice-free lakes. North American loons winter along the Atlantic coast from Newfoundland to Florida, around the Gulf of Mexico and along the Pacific coast from Alaska to Mexico. In Europe, several thousand great northern divers winter around Britain, Ireland, Norway and other Atlantic coasts. For the full story, read where do loons go in winter?.

Diet and diving

Fish make up about 80% of a common loon’s diet. Typical prey includes perch, sunfish, small trout, suckers, minnows and other fish up to about 26 cm (10 in) long. Loons also take crayfish, crabs, snails, leeches, frogs and aquatic insects, and in winter they catch marine fish such as herring and flounder.

Loons are superb divers. Unlike most flying birds, they have solid, heavy bones rather than air-filled hollow ones, which helps them sink. They can also squeeze air out of their feathers and body to float lower or slip under the surface without a splash. Powerful legs set far back on the body drive them through the water, and they hunt by sight, so clear water is essential.

Most dives reach 4–10 m (13–33 ft) and last under a minute, but loons have been recorded as deep as 60–70 m (200–230 ft). They swallow most prey underwater.

The same legs that make loons great swimmers make them clumsy on land. Find out why in why can’t loons walk?.

Calls and behavior

The common loon is famous for its voice. It has four main calls:

• Wail: a long, rising, wolf-like call used to keep in touch with a mate or chick.
• Tremolo: a wavering, “laughing” call given when alarmed, and the only call used in flight.
• Yodel: a long, rising call given only by males to defend their territory.
• Hoot: a soft, short contact call within a family.

Loons call most often on calm nights in late spring and early summer. Learn what each sound means in what does a loon sound like?.

Breeding pairs defend a whole small lake or a bay of a larger one, and they can be aggressive toward intruding loons, ducks and other waterbirds. In late summer, groups of loons, mostly non-breeders, sometimes gather on lakes in social groups.

Reproduction and life cycle

Loons usually first breed at around 6 years old. Pairs return to their lake soon after the ice melts in spring, often with the male arriving first. Both birds build a nest from mud, grass and water plants right at the water’s edge, often on an island or a floating mat of vegetation, so they can slide straight into the water.

The female lays two eggs (sometimes one), olive-brown with dark spots, usually in May or June. Both parents incubate for about 28 days. The chicks are covered in dark down and leave the nest within a day of hatching. They can swim and make short dives right away, and for the first two weeks they often ride on a parent’s back to rest and stay safe.

Both parents feed the chicks fish for weeks. The young can fly at 70–77 days old and leave the breeding lake in autumn, usually after their parents. Juveniles then spend two or more years at sea before returning north.

Lifespan

Common loons are long-lived. Studies of banded birds in North America show that adults survive well into their 20s, with high yearly survival until about their mid-20s. Males aged 15 and older tend to lose condition and are more likely to be pushed off their territory by younger rivals.

Predators and threats

Adult loons have few natural predators, though bald eagles sometimes attack them on the nest. Eggs are taken by raccoons, skunks, mink, foxes, gulls, ravens and crows. Chicks are hunted by bald eagles, large gulls, snapping turtles and large fish such as northern pike.

Human-caused threats include:

• Lead poisoning from swallowed lead fishing sinkers and jigs, which loons pick up while looking for small stones to grind food. In New England, lead tackle has been one of the leading causes of death in adult loons, and several states restrict lead tackle.
• Mercury and acid rain, which build up in lake food chains and can reduce breeding success.
• Shoreline development and boating, which destroy nest sites and swamp nests with boat wakes.
• Oil spills and fishing nets in their winter range at sea.

Conservation status

The IUCN lists the common loon as Least Concern, with a large population of roughly 600,000 birds and an overall stable trend. Over half of North America’s breeding loons nest in Ontario and Quebec. Europe has a much smaller breeding population, mostly in Iceland, of roughly 1,400–2,600 mature birds.

Local declines still worry biologists. Long-term studies in Wisconsin and other areas show falling chick survival, linked partly to lower water clarity. Volunteer loon watch programs, floating nest platforms and campaigns to switch to lead-free tackle are helping in many places. The southern edge of the breeding range has also shifted north over the past century.

Loons, grebes and ducks: what is the difference?

Loons are often mistaken for ducks or cormorants, but they belong to their own ancient order, the Gaviiformes, with only five living species: the common loon, the yellow-billed loon, the Pacific loon, the Arctic loon and the red-throated loon. All five live in the Northern Hemisphere. The common loon is the best-known loon in North America and the second largest after the yellow-billed loon.

Compared with a duck, a loon has a long, pointed, dagger-like bill instead of a flat one, sits much lower in the water and dives far more often and deeper. Grebes also dive for fish and have legs set far back, but they are smaller, have lobed toes rather than fully webbed feet and lack the loon’s bold summer pattern. Cormorants, which also hunt underwater, hold their hooked bills tilted upward and often perch with wings spread to dry.

Myths and facts

Myth: Loons mate for life. Loon pairs often stay together for several years, but they winter apart, and when an intruder evicts one partner, the other quickly pairs with the newcomer. Most loons have more than one mate over their lifetime.

Myth: The loon’s call is a cry of grief. The famous wail sounds mournful, but it is simply a contact call that helps mates and chicks find each other.

Fact: Loons are an old, distinct branch of the bird family tree. Fossil loons are known from millions of years ago, including several species from the Pliocene epoch, and loons are not closely related to ducks, grebes or cormorants.

Relationship with people

Few birds are as closely tied to wilderness in the public imagination. The common loon is the provincial bird of Ontario and the state bird of Minnesota, and it appears on Canada’s one-dollar coin, nicknamed the loonie. It also features in the stories of many Indigenous peoples, including an Ojibwe story in which a loon helps create the world.

The loon’s wail is so evocative that filmmakers use it constantly to signal a lonely lake or a wild night, sometimes in places where loons never live. See which other state birds made the list in our guide to US state birds.