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Our Common Loons

Of the five species of loons, the Common Loon Gavia immer is the species best known to most of us. Although it migrates to warmer areas around the Gulf of Mexico and the east and west coasts for the winter, in the spring it returns to northern lakes to breed when the ice melts.

Common Loon sounds

Anyone who has spent time in the northern woods has undoubtedly heard the haunting call of the Common Loon. There are four basic calls, which are heard mostly in the spring and summer. Each call has a different meaning.

Hoot - The hoot call is not as intense or as loud as the other calls. It is used to keep in contact with mates, chicks and social groups residing or visiting the same lake.

Tremolo - The tremolo has been described as "insane laughter;" it is 8 to 10 notes voiced rapidly and varying in frequency and intensity. This alarm call usually indicates agitation or fear, often caused by disturbance from people, a predator or even another loon. This is also the only call that loons make in flight.

Wail - The wail is most frequently given in the evening or at night, and can be heard for many miles. This haunting call is not an alarm call but is used to keep in contact with other loons on the same lake and surrounding lakes.

Yodel - The yodel is only made by male loons. This call is used to advertise and defend their territory, especially during incubation and early chick-rearing. If you are watching loons and they make this call or a tremolo, it usually means you are too close and are disturbing the loons. If that happens, you should leave their territory and give them their space.

Striking good looks
Common Loons are very striking with their black-and-white checkered back, glossy black head, white belly and wing lining, and characteristic white necklace around the throat. All loons have grayish feathers in the winter, and immature birds tend to resemble adult birds in winter plumage. The white feathers of the belly and wing linings are present year-round.

Males and females look the same, although males are generally larger. Adults are large-bodied, weighing from 6-14 pounds and measuring almost 3 feet from bill tip to outstretched feet.

The skeleton and muscular systems are designed for swimming and diving. Loons are streamlined. Their legs are placed far back on their bodies, allowing for excellent movement in water but making them ungainly on land. The head can be held directly in line with the neck during diving to reduce drag and the legs have powerful muscles for swimming. Many bones of the loon's body are solid, rather than hollow like other birds, aiding in diving ability. During dives, their large webbed feet provide all of the propulsion and the wings are held tight unless they are used to help make sharp turns while chasing prey.

Loons spend their time hunting, feeding, resting, preening and caring for their young. They are predators, preferring fish to other food, but they are known to eat aquatic vegetation, insects, mollusks and frogs. The life expectancy of a loon may be 15-30 years.

They're just resting
The bird spends long rest periods motionless on the water. It may rouse itself to stretch a leg or wing at intervals, occasionally comically waggling a foot. When swimming on top of the water a loon will sit erect with neck slightly curved. The loon will peer under water, moving its head from side to side to locate prey. It then aims and dives quickly. Loons will stay under water for almost a minute and can dive to depths of 260 feet. During the dive, feathers are compressed and air is forced from between the feathers and from air sacs in their bodies. Loss of air from the air sacs also allows loons to quietly sink below the water surface to avoid danger.

Adult loons may fly to different lakes to feed. The adaptations that make loons such efficient divers also make them heavy and slow to take wing. To take off from a lake, loons run along the surface into the wind. The distance needed to gain flight depends on wind speed; in calm times the birds may run as far as several hundred years before they gain enough speed to take off. Once in the air, the loon's relatively small wingspan (4-5 feet) carries it at average speeds of 74 miles per hour during migration. The wings beat quickly to carry the large body and have a high degree of curvature to provide lift.

Common Loons spend little time on land and have to pull themselves onto land to nest. They generally move one foot at a time to walk, shuffling along with their breast close to the ground. On return to the water, the loon slides in along its breast and stomach. At night, loons sleep over deeper water, away from land for protection from predators.

Loons like their space
Loons arrive in pairs on northern lakes in spring as soon as the ice thaws. Loons are solitary nesters. Small lakes, generally those between 12 and 125 acres, can accommodate one pair of loons. Larger lakes may have more than one pair of breeding loons, with each pair occupying a bay or section of the lake. Until recently, loons were thought to mate for life. Banding studies have shown that loons will sometimes switch mates after a failed nesting attempt, even between nestings in the same season.

Loons build their nests close to the water, with the best sites being completely surrounded by water, such as on an island, muskrat house, half-submerged log or sedge mat. Generally these birds can slip directly from the nest to water. The same sites are often used from year to year. Loons will use whatever materials are at hand to build their nests: tree needles, leaves, grass, moss and other vegetation have been found under loon eggs. Both the male and female help in nest building and with incubation, which lasts until hatching usually 26-31 days. If the eggs are lost, the pair may renest, often in the same general location.

Usually two eggs are laid in June, and toward the end of the month loon chicks covered in brown-black down appear on the water. Loon chicks can swim right away, but spend some time on their parents' backs to rest, conserve heat and avoid predators, such as large carnivorous fish, snapping turtles, gulls, eagles and crows. After their first day or two in the water, the chicks do not return to the nest.

Chicks are fed exclusively by their parents for the first few weeks of life, and up until eight weeks of age the adults are with them most of the time, providing most food. After this time the chicks begin to dive for some of their own food and by 11 or 12 weeks, the chicks are providing almost all of their own food and may be able to fly. Chicks are fed small food items early in their life including small fish, crayfish, minnows and some aquatic vegetation. At migration time, the young are able to look after themselves, and the adults generally leave first, with the young following soon after.

Lead kills
Loons routinely swallow small pieces of gravel on the bottom of lakes. The gravel passes to their stomach and helps in digestion, like grit in the stomach of a chicken. When fishing sinkers are lost during fishing and drop to the bottom of the lake, they can be picked up by loons or other waterfowl. Some loons also swallow fishing jigs when they mistake them for minnows. As the lead sinker or jig is exposed to stomach acids and to other pebbles, lead enters the bird?s system and slowly poisons the bird.

You can help by giving nontoxic sinkers a try. The less lead we release into the environment, the better off our wildlife will be. Currently there are many non-toxic sinker alternatives on the market made of bismuth, tin, stainless steel, tungsten, ceramic, recycled glass and natural granite.

People can be a nuisance
Another area of concern relates to low breeding success. The loon is susceptible to the effects of pollution, development and disturbance. Loss of breeding habitat and disturbance are probably the main causes of the reduction and abandonment of breeding sites. Loss of habitat results from lakeshore development and spills of oil and other pollutants. Physical interference with nests or young and increased boat wakes on lakes, which may swamp or destroy nests, also cause loons to abandon some nesting sites, allowing the eggs to chill and die. On busy recreational lakes, motor wakes sometimes drown chicks. Loons occasionally get tangled in discarded fishing line or plastic six-pack holders, dooming them to slow starvation.

Recent studies have indicated that loon nesting success and survival of young may decrease with increased lake acidity, the result of acid rain. Acidity can result in decreased fish and other foods, causing loon chicks on very acid lakes to starve. A high concentration of mercury is also an area of concern.