Common Loons and Citizen Science in Glacier National Park
Why We Care
With its iconic wail, the Common Loon conjures up images of wilderness, solitude and remote northern lakes.
The haunting calls and stark beauty of the Common Loon are like no other. And, just as this iconic bird conjures up images of wilderness, its survival depends on the persistence of wild places. Due to their sensitivity to disturbance and their need for pristine habitat, Common Loons also serve as indicators of lake ecosystem health. Concerted management efforts, including habitat conservation and minimizing loon disturbance, are critical for the continued success of these remarkable birds.
A loon sitting low on its nest, preparing to dive into the water.
Loon preparing to flush off its nest due to disturbance.
The beautiful profile of a common loon in breeding (alternate) plumage is shown.
A group of citizen scientists learning how to use a GPS unit.
Adaptations
Loons are members of one of the most ancient orders of birds still in existence, having evolved over one million years ago. Loons have evolved with an amazing array of adaptations, making them well suited and highly specialized for their unique niche in the environment. This specialization comes at a cost, though, since loons are not able to adapt to a changing environment as easily as some other species.
Side profile of a common loon.
Range
The Common Loon is found throughout North America at different times of the year. Near the southern extent of their range, they can be found on pristine freshwater lakes throughout the Crown of the Continent Ecosystem during breeding season (early spring through fall); migrating to coastal areas for the winter.
A topographic map of the Crown of the Continent Ecosystem outlined with the text "The Crown of the Continent Ecosystem encompasses over 10-million acres of some of the most intact wildland in North America. It is an essential home for a multitude of wildlife."
Glacier National Park sits in the heart of the Crown of the Continent Ecosystem which extends through Alberta, British Columbia, and Montana, providing some of the most ecologically diverse landscape in North America.
The map below shows loon migration throughout the year using data collected by citizen scientists participating in eBird, a Cornell Lab of Ornithology citizen science project.
A GIF depicting loon breeding abundance as in changes throughout the year in North America.
Each fall loons migrate from their breeding lakes in the north to coastal areas where they spend their winters.
Threats
Throughout their breeding and migration range, loons need adequately protected habitat to survive and produce offspring.
The data from Glacier's Citizen Science Program helps determine threats to loon population health and gives park managers the information needed to make informed management decisions.
A loon with two chicks riding on its back.
A close up of a two-day old loon chick.
In addition to slow breeding rates and difficulty in dispersing to new areas, loons face a series of natural and human-caused threats to their survival and breeding success. This is especially true in areas such as Glacier National Park that are near the edges of the loons' breeding range.
With our expanded access to remote lakes, the Common Loon has become increasingly impacted by human disturbances.
A photo of the Many Glacier Hotel on Swiftcurrent Lake with mountains and ominous clouds looming overhead.
A photo of a motorboat on a lake with a mountain backdrop.
Loon Citizen Science
In 2005, park biologists and Crown of the Continent Research Learning Center staff created the Common Loon Citizen Science Project. This project engages trained volunteers and staff to track Common Loon population trends and reproductive success across Glacier National Park’s one million acres.
With initial support from the Glacier National Park Volunteer Associates and ongoing support from Glacier National Park Conservancy, this program continues to inform park management about how to protect its loon population.
Citizen Scientist showing a young volunteer how to use the spotting scope.
Each year, citizen scientists contribute a tremendous amount of hours to ensure all lakes are surveyed. Here is an infographic explaining what an average year looks like:
Loon Population
The resident population is determined at the end of each season after reviewing the complete data set across 45 priority lakes. At the end of the monitoring season each year, we confirm known nest locations, nest failures, and successfully hatched and fledged chicks.
The figure below depicts the resident loon population in Glacier National Park from 2006 to 2023, determined by replicating surveys at breeding lakes and incorporating data from the annual Loon Days event. Although some variation in population is normal, managers can be alert to any sudden dips or sustained downward trends by monitoring these data over time.
Glacier's Loon Habitat
While Common Loons in Montana represent only 1% of the global breeding range and Glacier National Park harbors only 20-25% of those loons, the park provides Common Loons with critical habitat. Thanks to the considerable effort contributed by citizen scientists, we have learned that each lake we monitor plays a role in providing for the survival of this special species.
Understanding the benefits that individual lakes provide allows us to prioritize and target conservation measures. Glacier National Park provides three important habitat types for loons.
A pair of loons swimming near their nest.
Breeding Lakes
In Montana, breeding habitat is restricted to lower-elevation, forested lakes in the northwest corner of the state. Successful nesting sites require shelter from wind and disturbances. Nests are located within a few feet of the water’s edge and can be easily upset by changes in water levels.
Glacier contains 138 named lakes; only a handful meet the criteria of a suitable breeding lake.
North Fork
Underwater photo of Westslope Cutthroat Trout swimming.
A photo of a lake.
One area of Glacier National Park that provides great breeding habitat for Common Loons is in the northwest part of the park; an area referred to as the North Fork. Lakes in the North Fork “check all the boxes” when it comes to loon habitat:
☑ Fish found in these lakes provide a great food source.
☑ They are surrounded by boreal forests acting as wind breaks.
☑ The geographic position means an earlier thaw time in the spring.
Potential Breeding Lakes
Potential breeding lakes are important habitat for loons because they provide all the necessary criteria that a loon needs to breed. The main difference of potential breeding lakes is that no confirmed evidence of breeding exists on these lakes at this time.
If breeding occurs on these lakes it demonstrates that loons are dispersing to new areas and may indicate growth in the population.
For this reason, we put significant effort into engaging our citizen scientists in surveying potential breeding lakes to document new breeding areas.
Northeast Glacier
Female observer sites in a canoe with binoculars scanning the lakeshore.
An adult bald eagle swooping low with talons extended above the lake.
Adult common loon swimming with two-day-old chicks.
By using citizen scientists in this project, we can better document why breeding is less successful in the northeast part of the park. The data collected provides necessary information to determine if management actions might improve nesting success or if natural factors, beyond our control (e.g. natural water level fluctuations, predation, etc.), are the underlying cause of limited breeding success. Understanding what role these lakes play in the overall reproductive success of Glacier’s loon population is integral to ensuring the success of Common Loons in the park.
Foraging Lakes
Foraging lakes are integral to Glacier's loon population.
Foraging lakes are important to loon conservation because they help to supplement food sources, particularly for breeding pairs with chicks who can consume one thousand pounds of fish per summer. Each foraging lake can help sustain numerous breeding pairs.
Pairs that nest on small lakes, or lakes with low prey density, often use an adjacent lake for additional foraging.
A loon chick getting fed by an adult loon while riding on the back of another adult.
Foraging lakes are also important for adults who lack an established territory. Around the age of three or four, loons come back to the place they were born to try to establish their own territory. However, this can take several years. Foraging lakes are important congregation sites that loons can occupy safely while they wait to find a suitable, and unoccupied, breeding lake.
Lake McDonald
Close up photo of a Cutthroat Trout head underwater.
Common loon feeding a chick fish.
A group of four loons swimming.
We put effort into monitoring foraging lakes because a large portion of the park's loons use them.
Compared to other parts of the country, Glacier's lakes produce less fish and other food sources because of their low temperatures, extreme depth, and types of minerals supplied by surrounding rock.
These glacial lakes are oligotrophic, meaning they are relatively low in plant nutrients and contain abundant oxygen in the deeper parts. They are easily altered by small amounts of pollution, and therefore serve as bellwethers for the park’s overall water conditions.
Protecting Loons
Due to their range, naturally low reproductive rates, and heightened sensitivity to human disturbance during the breeding season, Montana’s Comprehensive Fish and Wildlife Conservation Strategy ranks loons as a Tier 1 species–a species with the greatest conservation need. They are also ranked as a Species of Concern in Montana by the U.S. Forest Service and Bureau of Land Management.
Evidence of the loon's ability to adapt to human activities, if given adequate breeding habitat and protection during breeding, suggests that properly designed conservation efforts can be beneficial.
Close up of loon with fishing line and lure hanging out of its mouth.
Two people looking across Lake McDonald at the Howe Ridge fire in the nighttime.
Gravel hiking trail winding through a lush forest.
Larger-scale management actions can involve working with developers, landowners, and local water control agencies to address risk factors to nesting territories from human impacts. Continuing education, research, and monitoring efforts are also important long-term management actions.
The Citizen Science Program has produced tangible conservation outcomes in the form of cautious management decisions within Glacier National Park.
Loon Banding
Banding efforts are critical in researching movement of Common Loons in Glacier National Park and throughout Montana. By marking birds with unique color-coded bands, researchers can identify individual loons. This allows us to estimate factors such as loon dispersal, territory upheaval, mate fidelity, and survival rates within Glacier National Park.
Loon taking off on lake showcasing bands on legs.
What Can We Do?
Common Loons are an iconic piece of our landscape. They help to shape the lakes and lands that we love to enjoy. With your help, we can preserve loon habitat in Glacier National Park and the surrounding area so that these majestic birds continue to grace our northern forests with their presence and their ancient wail.
Steps small and large can be taken to preserve loon habitat. Whether it’s how we choose to recreate, practicing "leave no trace" principles, or participating as a citizen scientist, everyone can do their part to keep this incredible species in Glacier.
Two people fly fishing on a lake.
A loon with its beak twisted in fishing line.
A loon sitting low on its nest, preparing to dive into the water.
Loon preparing to flush off its nest due to disturbance.