Common Loons

Common loon with crayfish - Derrick Jackson/Boston Globe.


Common loons are listed as a threatened species in New Hampshire. Since loon monitoring began in 1976, populations have slowly increased due to conservation efforts.


The common loon is approximately 24 inches in length, with a wingspan of 58 inches. Their heads and necks are black, while the throat has a band of small patches of white. The loon's back has a black background with white markings. The underside of the body is white. During the winter, a loon's plumage is less colorful. Upper feathers are dark gray, while the underside remains white.


Loons breed in North America from Alaska south to Massachusetts. New England loons primarily winter off the Atlantic coast, from Maine to Long Island Sound.


Loons spend the winter in coastal waters and return inland to breed shortly after spring ice-out (generally April though early May). Since loons have difficulty walking on land, due to the posterior position of their legs, they generally build nests close to the water's edge. Nests are constructed on the ground, and are often built on hummocks or small islands, where they are protected from predators. Nests may be mere scrapes, or may incorporate submerged or emergent vegetation.

Eggs: One or two dark-colored eggs are laid each year.


Loons feed primarily on fish, but will also take other aquatic vertebrates and invertebrates, such as crayfish. Foraging is usually confined to relatively shallow areas, less than 15 ft. in depth. Yellow perch and pumpkinseed are often preferred forage species, in this area, possibly because they tend to be found in shallower waters, and their behavior makes them easier for loons to see and catch.

Threats to Loons


Loons generally return to the same nest site each year, unless they are disturbed or their habitat is degraded. Increased human activity in an area can cause loons to abandon nesting sites, and can result in incubating birds leaving their nests, thus exposing vulnerable eggs to predation. Boat wakes may force water into nests and flood them. High speed watercraft sometimes kill or injure chicks or adults due to collisions. Boats may also get between chicks and adults, causing them to separate and exposing chicks to increased risk of predation.

What You Can Do to Avoid Disturbing Loons

You can help avoid disturbing nesting loons by keeping your distance from likely or known nest sites (marshy or boggy shores, river backwaters, small islands). A good rule of thumb is to try to stay at least 400 feet or more away from nest sites, or from any loons that are showing signs of 'distress' or disturbance.

Here are some loon disturbance behaviors to watch for, that indicate you are getting too close:

  • Brow of bird is a 'square' shape, rather than smoothly rounded.
  • Bill is pointed up, neck is stretched up, bird looks alert.
  • Bird 'dances' upright on the water, while flapping wings.
  • Bird's neck and body are stretched out low on nest (or on water)
  • Bird makes a 'tremolo' (laughing sound) or 'yodel' call.

If you observe any of these behaviors, please make sure you increase the distance between yourself and the loon.

Fluctuating water levels 

Loons build nests mid-May through June. Fluctuating water levels during this time can result in nest failure. Rising water levels can flood nests and cause them to be abandoned, while decreasing water levels can make nests inaccessible to the loons.

Fishing line, hooks and lead sinkers

Loons have been known to get tangled in fishing line left behind by fishermen. Once a loon becomes entangled, it is very hard for them to free themselves. Loons also swallow hooks. One of the biggest threats to loons comes from lead sinkers. Loons swallow sinkers thinking they are pebbles they need to aid digestion. A bird with lead poisoning displays physical and behavioral changes and their ability to fly becomes impaired. Once a bird becomes weak, it is more susceptible to predation; it has a harder time finding food and nesting.


Mercury is a toxin known to cause abnormal behavior, physiological damage and death in loons. Mercury is a natural- occurring element in the environment, but current deposits are at a level 2-5 times the normal distribution. It is traced to coal burning power plants and incinerator emissions. In waters where loons have high levels of mercury in their blood, their productivity is below average. It is estimated that 21-35% of common loon breeding populations in New England have high levels of mercury. Mercury testing in the Umbagog Lake area has shown elevated levels of mercury in loons.

Loons of the Umbagog Area

By the early 1900s, nesting loon populations had decreased drastically. This was due, in part, to people shooting them and collecting their eggs for sale. Since 1918 loons have been legally protected. In-depth studies of loons in the Umbagog Lake area began in 1976 and have been on-going ever since. The area has one of the higher populations of nesting loons in New Hampshire. In recent years there has been an apparent decrease in the number of loon territories on the lake, for unknown reasons.

Refuge loon nests are protected with signs and float lines to block off areas where nesting is active. These float lines keep boat traffic to a minimum around the nests and help to ensure loons aren't frightened away from their nesting areas. Please respect these float lines and do not cross over them.

Loon Calls

Loons have four different calls: the tremolo, wail, yodel and hoot.


This is usually a call that signals other loons to flee the area. Diving under water, doing a surface run, or taking off usually follows this call. This is the only call loons do while in flight.


This is sometimes called the night call. The wail is most commonly used to re-establish contact with its mate. For example, if loons want to exchange places with their mate on a nest, they will wail.


Male loons are the only ones that use this call. It is used as a territorial defense.


This is most generally used between loons of the same family. It is used to "check up" on family members, as if to say, "are you doing OK?" The call lets other loons know of its whereabouts.


Evers, David, P. Reaman. 1997. A Comparison of Mercury Exposure and Risk Between Artificial Impoundments and Natural Lakes Measured in Common Loons and Their Prey iN 1996-1997. 1997 Field Season Report.

Foss, Carol R. 1994. Atlas of Breeding Birds. Audubon Society of New Hampshire. 2-3.

McIntyre, J.W. and J.F. Barr. 1997. Common loon (Gavia immer). The Birds of North America, No. 313.

Taylor, Kate, H. Vogel, J Kozaka. 2000. Loon Population Survey and Management Report Errol Dam Project-FERC No. 3133