The Common Loon (Gavia immer) is an iconic North American waterbird, recognizable by its striking black-and-white breeding plumage and its haunting, distinct calls echoing across northern lakes. These birds exhibit strong site fidelity, often returning to the same lake and territory to breed. Loons are built for an aquatic life, with their legs set far back on their bodies, which makes them masterful divers but renders them extremely clumsy on land. This anatomy, coupled with their long takeoff and landing requirements, dictates that their nesting location must be very specific.
Required Aquatic Environment
The Common Loon’s breeding range is concentrated across the forested lakes of Canada and the northern tier of the United States, including states like Minnesota, Wisconsin, and Maine. For a loon pair to establish a territory, they require a suitable body of water that can sustain them throughout the breeding season. The ideal breeding lake is generally large, often over 60 acres, to provide adequate space for foraging and a long, clear surface for their characteristic water takeoffs.
The water itself must be clear, as loons are visual hunters and rely on being able to see their prey underwater. A healthy fish population is therefore a prerequisite for nesting success, and loons will forage in relatively shallow areas, typically within 50 to 150 meters of the shoreline. They also seek lakes with minimal human disturbance, as excessive boat traffic or shoreline development can force them to abandon a territory or prevent them from finding a proper nesting site.
Specific Nest Site Selection
Within the chosen body of water, the male loon selects the precise nest location, which is almost always situated extremely close to the water’s edge. Because they cannot walk well, the nest must be placed so the incubating adult can easily slip into the water for a quick escape from potential threats. They often choose sites with a steep drop-off immediately offshore, allowing them to approach the nest from underwater.
Preferred locations include sheltered spots on small islands, peninsulas, or floating bog mats and hummocks in marshy areas. These isolated sites offer better protection from mammalian predators like raccoons and skunks, which are more common near mainland shorelines. The nest itself is a simple mound built by both the male and female, composed of readily available materials such as mud, pine needles, sedges, and other aquatic vegetation found near the water. Nests are often reused for multiple seasons if the previous attempt was successful.
Protecting the Nesting Grounds
The loon’s need to nest right at the water’s edge makes the nest vulnerable to changes in water level. Natural or human-caused fluctuations, such as those from hydroelectric dams, can either flood the low-lying nest or leave it stranded far from the water, preventing the clumsy adult from reaching it. Shoreline development further reduces the availability of secluded, suitable nesting habitat, forcing loons into less ideal locations.
Human recreational activity is another major factor, as the wake from passing motorboats can swamp a nest and wash the eggs away. To mitigate these threats, conservation groups often deploy artificial nesting rafts in developed or managed lakes where natural sites are scarce or unstable. These rafts offer a secure, floating platform that rises and falls with the water level, directly addressing the problem of fluctuating water and providing a safer alternative to vulnerable shorelines.