Threats to Loons

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How You Can Help

Because of their frequent encounters with humans, especially during the breeding season, Common Loons have disappeared from some areas along the southern fringes of their breeding range and are threatened by recreational and residential development along lakeshores across much of their range. Common Loons are designated as either “threatened” or a “species of special concern” in much of New England (except Maine), the upper Great Lakes region (except Minnesota), and the western United States.

Among the reasons for their decline in these regions are loss of nesting habitat to shoreline development, the hazards of coexistence on lakes traversed by powered watercraft, ingestion of lead sinkers, contamination of freshwater lakes, loss of fish prey to acid precipitation, and fluctuating water levels on lakes managed for flood control or electric power.

These threats come in all shapes and sizes — from careless disposal of fishing line to depletion of food resources due to acid rain. Any effort to reduce the impact of human activity on loons, however great or small, though, is rewarded by the sight and sound of loons that return each year to their lake homes.

Habitat Loss Due to Shoreline Development

Loons return to traditional nest sites year after year. Buildings and boat ramps on islands and shorelines in proximity to a traditional loon nesting site can cause loons to abandon the site. Some of the activities that go on around lakeside cabins can disturb loons, too: allowing dogs to run or play near nests can cause nest abandonment or destruction of eggs, for instance.

What You Can Do

Be aware of where loons nest in your area. Try to protect nest sites by contacting your state’s loon protection affiliate or natural resources agency to obtain “loon alert” signs. Stay off loon nesting islands or away from shoreline nest sites. Participate in local land-use planning meetings to control shoreline development on loon lakes.


Loons use large lake areas for nesting, feeding, and raising their chicks. Nesting birds are easily disturbed by boat traffic, jetskis, and even canoes. Because loons nest on the water’s edge, wakes from speedboats can wash eggs out of nests. Additionally, the prolonged disturbance of slow-moving fishing boats that approach a nest and remain nearby for a long time may force an incubating loon off its nest. As a result, the developing loon chicks inside the eggs may die from exposure. Heavy boat traffic can cause some loons to abandon a nest permanently.

Thoughtless boaters have been known to chase and harass loons. Sometimes, loons are struck by boats and killed or injured. More often, harassed loons will be disturbed while feeding, reducing their ability to meet their nutritional demands, or chicks may be separated from their parents, a situation which places the chicks at risk of predation or exposure.

What You Can Do

Report intentional harassment to your local game warden. Try to get the boat registration number and a photograph of the offense. Educate your neighbors and visiting boaters or anglers about loons. Help post “loon alert” signs at marinas and boat launches. These signs are available from some state DNR offices, or from several NALF affiliates. Do not approach loons while they feed in open water or are with their chicks. Watch them from a distance! Slow down when passing nests, but don’t linger. If a loon is seen “dancing” upright or giving the tremolo call, STAY AWAY. These are signals of distress!

Fishing Line, Fish Hooks, and Lead Sinkers

Loons have been injured and killed from becoming tangled in fishing line or ingesting fish hooks. Loons are known to ingest lead sinkers, mistaking them for the pebbles they use to help grind food in their gizzards. Lead poisoning is a significant cause of loon mortality, as reported by researchers at a 1992 NALF conference: 14 of 222 loons in their study died from lead poisoning; 11 of these had lead sinkers in their stomachs.

What You Can Do

Don’t litter. Retrieve all fishing line, hooks, and sinkers you use or find. Educate others about the problem. Keep abreast of fishing regulations in your area and support changes to those rules that will protect loons.


Predation is a natural part of any healthy ecosystem, but some loon predators may benefit from their adaptability to human activities. Raccoons, gulls, crows, and ravens are the major predators of loon eggs and chicks. These animals are also scavengers on human refuse, and their numbers have increased as a result of the abundance of garbage near human dwellings. And humans often dwell near loons during the loons’ breeding season, bringing more predation pressure to bear on vulnerable nests and eggs.

What You Can Do

Keep litter cleaned up. Secure garbage cans. Keep pet food out of reach of scavengers.

Water Pollution

Lake water quality is affected by shoreline development, agricultural runoff, logging activities, sewage, and atmospheric pollution. Loons must see underwater to fish. If lakes become cloudy or choked with vegetation as a result of excessive nutrient runoff, loons may no longer be able to fish. Acidified lakes are unable to support fish. In some of these lakes loons attempt to raise their young, but cannot find enough food for them. The young may survive for a few weeks, sustained by a diet of aquatic insects, but without fish they eventually weaken and die.

What You Can Do

Become involved in maintaining good water quality in your lake through your local lake association. Build responsibly — if you’re thinking of building near a loon lake, plan septic service carefully and avoid clearing the lakefront. Support legislation to protect wetlands, control acid rain-producing pollution, and regulate the use of agricultural chemicals.