The Common Loon
by Jay Sharp
In its mournful, tremulous, yodeling, wailing and far-reaching calls, the common loon, speaking from an ancestry that reaches back 100 million years, evokes an era of primal wilderness. From its view near the top of the food chain, the bird reflects the health of its modern watery habitats—the threatening and growing presence of mercury, acid rain and destructive alterations.
Like the other four species of its genus, the common loon spends most of its life on the water—swimming, diving, fishing, preening and resting. It comes ashore primarily for breeding and nesting. It takes flight primarily for new forage, predatory escape and seasonal migrations.
- Anatomical Adaptations: The common loon – anatomically specialized for swimming and diving – has a long and streamlined body, something like a torpedo. Its web-footed legs, set near the rear of its body and modified in the structure of the bones, serve the bird far better for propulsion through water than for walking on land. Its skeletal structure, more dense than most other birds, reduces buoyancy and facilitates dives and underwater swimming. Its eyes, reddened by a retinal pigment that filters light, provide superior underwater vision.
- Size and Weight: According to Judith W. Mcintyre and Jack F. Barr, writing for Cornell's Birds of North America, the bird's size varies substantially across its geographic range, with its length varying from about 2 to 3 feet; its wingspan, from approximately 3 1/2 to 5 feet; and its weight, from 5 to 15 pounds. In any part of its range, the male is larger than the female, weighing perhaps 25 percent more.
- Plumage: The male and female common loons have similar plumage. In its summer breeding plumage, the bird has a black head, a black stiletto-like bill, and two distinct collars—one, a band of black and white vertical stripes, and the other, a band of solid black. It has intense black and white checkering on its back and wings and solid white on its under parts. After changing to its more drab non-breeding winter plumage, it has a lighter-colored head, bill and neck. It has gray to grayish brown upper parts and white under parts.
- Locomotion: Supremely adapted for swimming, the common loon – propelling itself with its feet – can dive to depths of 200 feet or more and remain underwater for five minutes, although, on average, the bird stays submerged for no more than a minute. On land, the bird, with its rearward legs, can move only clumsily and off-balance across the land and it cannot take flight at all. To get airborne, the bird requires a long "runway" across the surface of the water, but once in the air, it can beat its powerful wings 250 times a minute and maintain steady airspeeds of 75 miles per hour or more, according to the Michigan Department of Natural Resources. At that speed, it may cover several hundred miles per day during migratory flights.
- Vocalizations: The common loon, according to Mcintyre and Barr, has a wide repertoire of calls, including a short low-amplitude hoot, a short higher-pitch toot, a short soft mating mew, a moderate-length one- to three-note wail, a high-amplitude and rapidly modulated laughing call or tremolo, and a high amplitude variable yodel. Each male delivers an individualized yodel—the signature vocalization of the common loon. In the quietness of evening in the wilderness, it can be heard yodeling 10 miles away.
Distribution and Migration
According to Mcintyre and Barr, the common loon breeding range extends eastward from Alaska across Canada to Greenland and Iceland and southward from the North American Arctic to the Great Lakes region. With the coming of winter, the bird – a medium-distance migrator – follows primary routes across eastern Canada and the United States and westernmost Canada and the United States to the coastal waters of North America's Atlantic shores, the northern Gulf of Mexico and the Pacific. It winters as far south as the Mexican states of Nuevo Leon on the Gulf Coast and Jalisco on the Pacific coast.
Habitat and Diet
In its breeding range, the common loon prefers lakes with secluded coves, islands, clear water and abundant small prey fish. It also, however, makes its home on reservoirs and quiet river waters provided that there is enough room on the water surface for it to launch its flight. For nest sites, said Mcintyre and Barr, the bird seeks the sheltered side of an island, the leeward side of the mainland or floating bog inlets. It prefers the water's edge, especially if it provides good coverage with a screened view. It will also use artificial nest sites. In its wintering ranges, the bird seeks out coastal bays and coves and estuaries, particularly those where the clarity, depth and salinity of the waters yield rewarding forage. The common loons, said the Seattle Audubon Society, "generally eat small fish up to 10 [inches] long, and also take crustaceans, mollusks, aquatic insects, leeches, and frogs. They may also occasionally eat aquatic plants."
Behavior and Life Cycle
When foraging, primarily during the day, the adult common loon may hold its head underwater, eyes open, to scan for prey, or it may dive underwater, eyes open, to forage for prey. Propelled by its powerful web-footed legs, it swiftly pursues fish through the water. It uses its bill to snatch its quarry, which it often swallows, head first, while submerged. It may bring larger prey to the surface, manipulating the catch so it can be swallowed head first. It may bring other prey to the surface to feed – bill to bill – to chicks.
When not foraging or parenting during the day, a common loon typically preens, bathes, rests or naps, often in open waters. At night, it rests and naps, again, normally in open waters.
Arriving at breeding ranges in the spring, common loons soon form pair bonds, which they may renew annually for years, say Mcintyre and Barr. At a site chosen by the male, the two construct a new nest – oval or circular in shape and a couple of feet across, near the water's edge – or they may refurbish an old nest. During courtship, they dive together, swim circles and dip bills. One calls for its partner with soft mewing as it heads for shore, where the two will join and mate.
Meanwhile, the male, especially, becomes very territorial. Two males often battle underwater, where the birds try to impale each other in the stomach with their stiletto-like bills. Sometimes one bird will inflict a fatal injury on the opposing bird.
Some days after mating and nest completion, the female lays a pair of 3-inch-long, olive to brownish splotched eggs, which both parents will incubate. They turn the eggs when one partner relieves the other on the nest.
After about a month, according to the National Geographic Society, the chicks begin to peep from within the eggs to announce their impending hatch. Soon, in the order in which the two eggs were laid, the two chicks – with black down-covered backs and white down-covered bellies – emerge from their shells.
True to its species, said Mcintyre and Barr, the common loon chick soon takes to the water, often within its first day, swimming with its parents. Although dependent on the parents for food, the chick begins diving and chasing minnows within a couple of days. While a chick may take refuge on a parent's back or beneath a parent's wing during the first few weeks, it grows and develops rapidly, becoming fully feathered and nearing adult size, able to fly, in less than three months, when it becomes essentially independent.
In early to late fall, a chick, now nearly grown, will join the common loon migration, including nearly three quarters of a million birds, to wintering grounds. It may not return to the summer breeding ranges for several years. If a chick survives to adulthood, it will reach sexual maturity at about five to seven years of age, said the Seattle Audubon Society. It may live until it is 30 years old.
During its lifetime, the common loon faces a panoply of hazards. According to the Michigan Department of Natural Resources, only one out of four chicks survives to adulthood since "…most chicks are lost to large turtles, predatory fish, hawks and eagles," predators which strike unexpectedly from various directions. Moreover, said Mcintyre and Barr, lake contamination as well as "by-catch from commercial fishing, direct take through subsistence hunting, marine oil spills, botulism outbreaks, and emaciation syndrome" have taken a toll on the common loons in some areas, for instance, in Washington and in several northeastern states, where it is listed as a "sensitive species" or "species of special concern."
While the overall population may be in decline, the International Union for Conservation of Nature and Natural Resources says that because the bird has an "extremely large" range and a "very large" population, the common loon is regarded as a species of "least concern."
- The dense-boned common loon can compress its feathers around its body and express the air from its lungs then move through the water with only its head above the water, like a periscope, according to the Michigan Department of Natural Resources.
- On the surface of the water, the common loon propels itself by stroking its feet alternately; underwater, it propels itself by stroking both feet simultaneously, according to Mcintyre and Barr.
- Since, typically, the common loon does not reach sexual maturity until it is five to seven years old and the hen lays only a couple of eggs per season, it is a bird of "low productivity, making it harder for the population to rebound from declines," said the Seattle Audubon Society.
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