Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

Loon on lake © Stephen J. Lang

To take flight, loons may run as far as a quarter of a mile on the water's surface to build enough speed to get aloft.
© Stephen J. Lang

February 2013

The uncommon loon

Volunteers and wildlife biologists work to conserve a remarkable bird.

Glenda C. Booth

The haunting, melancholy call of the common loon has long enchanted those who love to be near the water. The call can be a wobbly, liquid chortle or an eerie yodel, sounding almost unearthly, especially when it ripples through the quiet wilderness or echoes across a tranquil lake. Known as the "spirit of the wilderness," the common loon (Gavia immer) actually has four calls: the wail, yodel, tremolo and hoot. Common loons breed and raise their young in Canada and northern U.S. states, including Wisconsin, every summer.

Some good news

Wisconsin has some good loon news. Breeding loon numbers are rising and the total state loon population according to LoonWatch has grown from 3,017 in 1995 to 4,010 when estimated in 2010. LoonWatch is a program of the Sigurd Olson Environmental Institute that protects common loons and their aquatic habitats through education, monitoring and research.

"Wisconin has an increasing loon population whose growth rate has increased by over 25 percent in 15 years," says Michael Meyer, wildlife toxicologist and research scientist for the Department of Natural Resources. "We are seeing higher densities of nesting pairs on lakes and we are seeing loons using lakes that they haven't used for decades, plus there is a suggestion they are expanding southward."

And rates of mercury exposure in Wisconsin's loons are not as high as rates in the loons of some northeastern states.

What is a loon?

Loons are listed first in North American bird field guides because they are the most primitive bird, having existed long before humans. Adults have a black velvety head, red eye, sleek torpedoshaped body, black-and-white checkered back, a white "collar" on the back of the neck and a pointed bill that they hold parallel with the water. In winter, their plumage turns dark gray. Loons' legs are short and set far back so they cannot walk well. They weigh between six and 12 pounds.

Loons swim low in the water because their bones are heavy. Excellent divers, they can vanish underwater to find food or escape danger without leaving a ripple and reach depths of 200 feet or more. Their large webbed feet act as propellers, enabling fast travel underwater. The record diving time for the common loon is three minutes. The average diving time is 42 seconds, according to Darwin Long, avian biologist and aviculturist with the Audubon Nature Institute. A scientist who has conducted dive feeding studies, Long can pinpoint when a loon is about to dive.

"Watch him slim down. He exhaled," Long told a group of volunteers who were studying loons in the Gulf of Mexico last winter.

To take flight, loons may run as far as a quarter of a mile on the water's surface to build enough speed to get aloft. In the air, they have a rapid wing beat and can fly up to 75 miles per hour.

Loons preen to stay attractive, enable flight, protect against the elements, reposition feathers and to remove parasites, dirt and oil from their feathers. They collect oil from a large oil gland on top of the base of the tail and spread it over their feathers to make their bodies water- repellent.

Loons are sexually mature at age three and, on average, obtain their own breeding territory around age five. A pair always builds a nest near water, preferring islands to avoid predators, but also anchored to the mainland in wetland areas. Nest sites are somewhat open so they can see intruders. The female usually lays two eggs, which the parents-tobe take turns incubating 30 to 32 days. Loons are considered to be very territorial; they aggressively defend their nests and young. Adult loons have been documented to live over 25 years in the wild.

Two loons on th water; Paul Lueders
The Ojibwe (Chippewa) Indians called the loon "Mang" or "the most handsome of birds."
© Paul Lueders

Meyer, who has studied loons for more than two decades, says the number one reason loon nests fail in Wisconsin is predation.

"Nest abandonment due to personal watercraft or nest flooding due to wake action does occur," Meyer says, "but much less frequently than predation."

Loon chicks are semi-precocial, they leave the nest within two days of hatch, locomoting behind the adults or riding on their backs. The parents do feed them nearly exclusively for the first eight weeks.


In late October and early November before lakes freeze, loons fly south to coastal seas, with some traveling 3,800 miles. Loons are one of the few birds found in both freshwater and salt water, from northern lakes to southern marine environments.

Loons migrate south their first autumn and do not return to their breeding area for three years on average, says Andrew East, who has studied loons as a field biologist in Wisconsin and other states. Scientists are trying to understand where loons go during that time.

From mid-January to February, adults have a "catastrophic" molt, losing all feathers and becoming flightless for three to four weeks.

"Winter is stressful for loons because new feathers are growing and they are having a complete molt," explains Jim Paruk, director of the Center for Loon Conservation at Maine's Biodiversity Research Institute.

Loons return to northern lakes and rivers sporting their distinctive plumage usually in April or early May to breed and raise their young. Most migrating loons will return to the same area within 30 miles of their birthplace, East maintains.

Loon conservation research

Several Wisconsin-based scientists are probing multiple mysteries of this iconic bird.

Among those mysteries is migration. Kevin Kenow, a research wildlife biologist with the U.S. Geological Survey (USGS), studies common loon migration by tracking the birds' movements with satellite telemetry. Recently, he implanted 15 satellite transmitters on loons that breed and spend their summers on Wisconsin waterways. The transmitters are programmed to provide location information for about one year, but usually last around two years so he can monitor a loon's movements that long. During the fall and spring migration, the transmitters send information every day; in the winter and during the breeding season, every three or four days.

In the summers of 2010 and 2011, Kenow put transmitters on 31 adult loons in Wisconsin, Minnesota and Michigan's Upper Peninsula. The loons he tracks winter in the Gulf of Mexico off the Florida coast and in the south Atlantic off the Florida, Georgia and Carolina coasts. A few loons wintered on reservoirs in Kentucky and Indiana.

"This study will help managers better understand how loons fare as they head to their wintering grounds along the Gulf of Mexico and Atlantic coasts," said Kenow. "Right now, little is known about movement and habitat use along their entire migratory routes."

You can track the movements of individual loons during their migrations by logging on to the USGS website

Kenow is also contributing to a study on type E botulism in water birds, including common loons, using the Great Lakes. Outbreaks of type E botulism have become more common since 1999, he has found, resulting in troubling dieoffs of fish and fish-eating birds.

From 2000 to 2010, in all the Great Lakes, 49,500 mortalities of fish-eating water birds were attributed to botulism. Half of these were common loons. By documenting movements of loons and use patterns on the Great Lakes, Kenow hopes to contribute to a better understanding of the ecological and physical factors that lead to botulism outbreaks.

Loon chick on parent's back. © Paul Lueders
Swimming in the cold water is hard on the chicks, so from time to time they hitch a ride on their parent's back.
© Paul Lueders

Understanding the loons' feeding patterns and exposure routes is critical to understanding their exposure to botulism. Type E botulism commonly affects fish-eating birds and is caused by the ingestion of neurotoxins produced by the botulism bacterium. The botulism toxin is produced when spores germinate under conditions of low oxygen, certain temperatures and rich nutrients and the bacteria are actively growing.

Kenow has been focused on loons in Wisconsin since 1996, initially developing radio-marking techniques.

On botulism, he says, "Outbreaks of type E botulism have produced die-offs of fish and fish-eating birds in the Great Lakes since at least the 1960s."

Results of his work are being used by scientists with the USGS Great Lakes Science Center in Ann Arbor, Mich. to guide their work in looking at botulism in sediments, invertebrates and fish.

"This type of research helps us better understand habitats loons use during migration and on wintering grounds and points out vulnerabilities in their life cycles to problems like disease outbreak, contaminant exposure (like oil spills) and habitat loss. All this contributes to a better understanding of knowing where bottlenecks are," he says.

His work has been funded largely by the Great Lakes Restoration Initiative, a project of USGS and the U.S. Environmental Protection Agency. Past loon research efforts have been funded by the Wisconsin Department of Natural Resources.

Meyer studies mercury

Meyer has studied Wisconsin loons' exposure to mercury for 22 years. Of wildlife species tested, common loons have the highest level of exposure because they spend all of their time on the water except when incubating eggs and in most habitats, they almost exclusively eat fish.

"Fish magnify the methyl mercury," Meyer says.

Mercury is a naturally-occurring element; however, its level has increased in Wisconsin aquatic systems over the past 100 years due to industrial activity such as coal burning for electricity and incineration of industrial wastes. Mercury in the air settles into water or it can be washed into water from the land. Micro-organisms can change it into methyl mercury, a highly toxic form that can build up or bioaccumulate in fish and animals that eat fish.

In one study, he and colleagues examined mercury in lakes in four northern Wisconsin counties Vilas, Oneida, Forest and Iron. They found that concentrations in the blood of Wisconsin loons declined between 1992 and 2000 and increased from 2002 and 2010.

Meyer attributes the increase in mercury concentrations to a change in lake hydrology because of an ongoing drought in northern Wisconsin that could have resulted in increasing the rate of methylation of mercury that had already been deposited. He notes that this phenomenon may be more a consequence of regional hydrology, not necessarily more mercury entering the environment.

"A small portion less than 10 percent of our loon population is exposed to levels of mercury in their food that poses a toxicity risk. This differs from New England and the Canadian Maritimes where larger proportions are exposed to levels associated with reduced reproduction," he explains.

Some studies have found negative effects of certain mercury exposure levels on common loon reproduction, hatching rates, immune function, behavior, oxidative stress and neural histology.

Wisconsin and the neighboring states of Minnesota, Michigan and Illinois have imposed mercury emissions reduction rules. Wisconsin coal-burning electric utilities are required to cut mercury emissions by over 70 percent by 2015.

As for future research, Meyer will synthesize his and others' work on a multitude of stressors that impact loons breeding in Wisconsin, including botulism, lead fishing tackle, climate change, mercury and development on lakes, with the goal of identifying which factors are most important to loon conservation. Fifty loon citizen scientists, a group comprising the Northwoods Loon Protection Program, assist Meyer in his research.. The citizen scientists help monitor loon productivity on over 75 lakes in northern Wisconsin and identify critical nesting habitat.

Visit DNR Wildlife and Forestry Research - Citizen Monitoring for more information

Unraveling other loon mysteries

Scientists at The Loon Project are searching for answers to other questions. Dr. Walter Piper studies the territoriality of common loons. Dr. Jay Mager analyzes yodels used for territory defense. They and others are researching topics like territorial takeover, fatal fighting and prospecting by non-breeding loons.

In a study of artificial nesting platforms, they found "a dramatic increase in hatching success among loons using platforms compared to loons using shoreline sites, chiefly because raccoons and other egg predators rarely swim out to floating platforms to consume loon eggs." But they also found "higher rates of aggression and territorial takeover on territories with platforms, indicating a greater likelihood of eviction for breeders on such territories."

Why do scientists study loons?

"Loons are a good indicator of a lake's ecotoxicology and health. By observing loons' behavior, we can monitor a lake's health because loons feed almost exclusively on fish," says East. "They are effectively at the top of the food chain and represent everything that's going on below, including the effects of chemical compounds like PCBs and mercury that pile up in fatty tissues, organs, muscle, blood and feathers. When a loon eats fish, the loon is ingesting compounds that biomagnify as they move through the ecosystem."

Loons also intrigue non-scientists.

"People associate loons with the Northwoods. People in Wisconsin have an affinity for beauty," says East. "Loons sing loudly in the night unlike mergansers that don't do much more than grunt. People have a truly emotional connection to loons because they are very alluring. They are a symbol of the north."

Loon Summer

Field Notes

If you enjoy learning more about loons and love loon photography, check out Sandy Gillum's book, Loon Summer. The book follows a territorial pair of common loons who spend their summers on a northern Wisconsin lake and go to extraordinary measures to protect their chicks. Woven into the tale is the thread of responsible stewardship. Gillum, an ecologist, writes, "My year does not begin January 1st, but begins with the first calls of the loon in springtime. What a wonderful new year celebration!"

The book was published in 2008 by Field Notes Press in Eagle River (ISBN: 978-0-9801201-0-3).

Learn more about loons

Learn more about mercury and its effects on the environment

Visit U.S. Environmental Protection Agency Mercury

Help loons

Visit the LoonWatch website at Northland College Sigurd Olson Environmental Institute

Visit the Earthwatch Loon Project in the Gulf of Mexico

Loon calls

All About Birds, Common Loon

Hear the Calls of the Common Loon

Glenda C. Booth is a freelance environmental writer from Alexandria, Va. She became interested in Wisconsin loons after studying the effects of the BP oil spill disaster on loons along the Gulf Coast.