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Common Loon

Gavia immer ORDER: GAVIIFORMES FAMILY: GAVIIDAE

IUCN Conservation Status: Least Concern

The eerie calls of Common Loons echo across clear lakes of the northern wilderness. Summer adults are regally patterned in black and white. In winter, they are plain gray above and white below, and you’ll find them close to shore on most seacoasts and a good many inland reservoirs and lakes. Common Loons are powerful, agile divers that catch small fish in fast underwater chases. They are less suited to land, and typically come ashore only to nest.

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At a GlanceHelp

Measurements
Both Sexes
Length
26–35.8 in
66–91 cm
Wingspan
40.9–51.6 in
104–131 cm
Weight
88.2–215.2 oz
2500–6100 g
Relative Size
Larger and longer-bodied than a Mallard, smaller and shorter-necked than a Canada Goose.
Other Names
  • Great Northern Diver (British)
  • Plongeon huard (French)
  • Colimbo mayor, Colimbo común (Spanish)

Cool Facts

  • The Common Loon swims underwater to catch fish, propelling itself with its feet. It swallows most of its prey underwater. 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.
  • Loons are water birds, only going ashore to mate and incubate eggs. Their legs are placed far back on their bodies, allowing efficient swimming but only awkward movement on land.
  • 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.
  • A hungry loon family can put away a lot of fish. Biologists estimate that loon parents and their 2 chicks can eat about a half-ton of fish over a 15-week period.
  • Loons are like airplanes in that they need a runway for takeoff. In the case of loons, 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.
  • Loons are well equipped for their submarine maneuvers to catch fish. Unlike most birds, loons have solid bones that make them less buoyant and better at diving. They can quickly blow air out of their lungs and 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.
  • Like many young birds, juvenile loons are really on their own after mom and dad leave at about 12 weeks. 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 years. In the third year, young loons return north, although they may not breed for several more years (on average they are six years old when they start breeding).
  • Migrating Common Loons occasionally land on wet highways or parking lots, mistaking them for rivers and lakes. They become stranded without a considerable amount of open water for a long takeoff. A loon may also get stranded on a pond that is too small.
  • The Common Loon is flightless for a few weeks after molting all of its wing feathers at the same time in midwinter.
  • The oldest-known Common Loon lived at least 24 years, 1 month, spending its summers on a lake in Michigan.

Habitat


Lake/Pond

Common Loons are a classic bird of the North Woods lakes. They are excellent indicators of water quality as they require crystal-clear lakes (which makes it easier for them to see prey underwater) with abundant populations of small fish. Lakes with coves and islands are preferred as they provide cover from predators while resting and nesting. They also require lakes with enough surface area for their flapping-and-running takeoffs across the water. In their winter range along ocean coasts, they occur fairly close to shore and in bays and estuaries. They are only rarely found more than several miles offshore. Some Common Loons winter inland, on large reservoirs and slow-moving rivers. Common Loons that migrate across interior North America find large lakes and rivers to move between on their way north and south.

Food


Fish

Common Loons are expert anglers. Their diet consists of mostly fish, particularly perch and sunfish on their northern lakes. If fish are scarce or water is too murky for fishing, they will catch crustaceans, snails, leeches and even aquatic insect larvae. Though people on the surface only see loons disappear with a dive and reappear with a fish in their bill to be swallowed headfirst, their fishing pursuits underwater are something to behold. Loons shoot through the water like a torpedo, propelled by powerful thrusts of feet located near the rear of their body. When their quarry changes direction, loons can execute an abrupt flip-turn that would make Olympic swimmers jealous: they extend one foot laterally as a pivot brake and kick with the opposite foot to turn 180 degrees in a fraction of a second. In their wintering waters, loons eat smallish fish such as Atlantic croaker. Sometimes they band together in groups to chase schools of Gulf silversides.

Nesting

Nesting Facts
Clutch Size
1–2 eggs
Number of Broods
1 broods
Egg Length
3.5–3.5 in
8.8–9 cm
Egg Width
2.2–2.2 in
5.5–5.7 cm
Incubation Period
26–29 days
Nestling Period
2 days
Egg Description
Brown with dark splotches.
Condition at Hatching
Covered with down, sooty black with a white belly. Able to swim and ride on parents’ backs within hours of hatching.
Nest Description

Male and female build the nest together over the course of a week in May or early June, making a mound out of dead plant materials such as sedges and marsh grasses that grow along the lake’s edge. Then one of the loons crawls on top of the mound and shapes the interior to the contours of its body. The finished nest is about 22 inches wide and looks like a clump of dead grasses by the edge of the water.

Nest Placement

Ground

The male selects the nest site. Loons nest in quiet, protected, hidden spots of lakeshore, typically in the lee of islands or in a sheltered back bay. Loons can’t walk well on land, so nests are built close to a bank, often with a steep dropoff that allows the bird to approach the nest from underwater. They also use artificial nesting platforms, which people have offered as alternative habitat on lakes with extensive shoreline development. Many times a nesting pair of loons will reuse the same site the following year, refurbishing their old nest instead of building a new one.

Behavior


Surface Dive

Common Loons spend a lot of their time working shallow waters for fish: swimming slowly and sticking their heads into the water to look for fish, then diving suddenly after their quarry with a quick plip! that hardly leaves a ripple on the water’s surface. Loons do all their feeding during the day, when they can best see their prey. At times, loons can be seen sticking one foot up out of the water and waggling it—this may be a means of cooling off, as scientists have observed loons waggling their feet more often on sunny, midsummer days. Loons also perform a territorial display of lifting their body upright and flapping their wings vigorously. Canoeists who get too close to a loon may witness this display, along with a defensive tremolo call as the loon swims away. Loons also tremolo when they fly from lake to lake or in circles above a lake, their necks sticking straight out and feet trailing behind them. They can be very vocally active with nocturnal choruses. After sundown, many North Woods lakes reverberate with the echoes of loon wails and yodels and tremolos (which writer John McPhee called “the laugh of the deeply insane”). In spring, loon mates arrive back on their lake separately. Loons are monogamous, and pair bonds typically last about 5 years. 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 and synchronous dives. If nesting is successful, loon chicks can be seen going for a ride around the lake on a parent’s back.

Conservation

status via IUCN

Least Concern

North American Common Loon populations are stable and healthy overall. However, Common Loons require clear, unpolluted lakes, and can be harmed by pollution and disturbances. Regional declines have occurred at the southern edge of their range. In the Midwest, loons have disappeared from breeding sites in Illinois, Indiana, Iowa, and Ohio, and are only found in northern areas of Minnesota, Wisconsin, and Michigan. Their range has retracted in New England as well, though loon populations have rebounded there thanks to restoration efforts. Lead fishing sinkers, which loons ingest when they scoop up pebbles off the lake bottom to store in their gizzards, have been a significant cause of loon deaths from lead poisoning. Mercury from the burning of coal can build up in lakes through rainfall, and this has led to poor reproductive success for Common Loons in Canada, New England, and Wisconsin. Common Loons are often caught inadvertently by commercial fishing nets, both on the Great Lakes and in the ocean. Acid rain can acidify lakes, reducing fish populations that loons depend on. Human activity, particularly motorboats, can disturb loons on breeding lakes. Ocean oil spills can cause die-offs on loon wintering waters. Scientists are monitoring satellite transmitters on loons to evaluate if and how they were affected by the 2010 Deepwater Horizon oil spill.

Credits

  • Evers, David C., James D. Paruk, Judith W. Mcintyre and Jack F. Barr. 2010. Common Loon (Gavia immer). In The Birds of North America, No. 313 (A. Poole, P. Stettenheim, and F. Gill, eds.). The Birds of North America Online, Ithaca, New York.
  • Benyus, J. Northwoods Wildlife: A Watcher’s Guide to Habitats. NorthWord Press, Minocqua, Wisconsin.
  • Dunne, P. 2006. Pete Dunne’s Essential Field Guide Companion. Houghton Mifflin, New York.
  • USGS Patuxent Wildlife Research Center. 2011. Longevity records of North American Birds.

Range Map Help

Common Loon Range Map
View dynamic map of eBird sightings

Migration

Medium-distance migrant. Common Loons migrate from northern lakes to coastal ocean waters. Loons in western Canada and Alaska migrate to the Pacific Coast, from Alaska’s Aleutian Islands down past Mexico’s Baja Peninsula. Loons from the Great Lakes region migrate to the Gulf of Mexico or Florida coasts. Loons from eastern Canada migrate to the Atlantic Coast.

Find This Bird

On a North Woods lake in summer, loons stick out conspicuously as large, tuxedoed birds swimming about in the middle of the lake. They can be very vocal and easy to locate, as the yodeling of one loon will often elicit a chorus response from other loons in the area. In winter, loons adopt a much quieter profile along coastal waters, wearing drab, gray plumage. They typically stay close to shore, though, so a scan out to sea with your binoculars will often reveal loons hidden among the waves.

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Spirit of the North: an intimate portrait of the Common Loon. Story and photos in Living Bird magazine.