Loons are aquatic birds known for their distinctive calls and remarkable diving abilities. Their streamlined bodies and powerful webbed feet make them highly efficient swimmers and divers.
Loons and Their Dual Habitats
Loons inhabit saltwater environments, though their presence is seasonal. During breeding, loons primarily reside on freshwater lakes and ponds across northern North America and Eurasia. These freshwater bodies provide suitable nesting sites, often on islands or secluded shorelines, and ample food for raising their young.
As winter approaches and freshwater lakes freeze, many loon species migrate to coastal marine environments. The Common Loon (Gavia immer), Arctic Loon (Gavia arctica), and Red-throated Loon (Gavia stellata) are examples of species that use both habitats. Juveniles often remain in these saltwater coastal areas for several years before returning to freshwater for breeding.
Reasons for Saltwater Migration
Loons migrate to saltwater environments due to factors like food availability and survival during colder months. When freshwater lakes freeze, their primary food sources become inaccessible. Coastal marine areas, in contrast, offer a consistent and richer supply of fish, crustaceans, and other marine invertebrates throughout the winter.
Coastal regions also provide ice-free waters, which are important for loons. These birds require a “runway” of open water to take flight due to their dense bones and rear-set legs, optimized for diving. Milder coastal temperatures ensure continuous access to open water for foraging and escaping predators, which is not possible on frozen inland lakes.
Their migratory patterns lead them to these coastal areas for wintering. For instance, Common Loons breeding in the Great Lakes region may migrate to the Gulf of Mexico, while eastern Canadian populations often winter along the Atlantic Coast. These seasonal movements are an important part of their life cycle, allowing them to exploit different ecosystems as environmental conditions change.
Coping with Saline Environments
Loons possess specialized adaptations that allow them to live in saltwater. The most notable of these are their supraorbital salt glands, located above each eye. These glands excrete excess salt ingested from their marine diet and the surrounding saltwater.
When loons consume salty prey or water, excess salt enters their bloodstream. This activates the salt glands, filtering out a concentrated salt solution. This solution then drips out through ducts to the bird’s nostrils, running down the beak and back into the environment. This process allows loons to maintain their internal water balance without becoming dehydrated.
Loons can drink saltwater due to this adaptation, but they prefer freshwater when available. The salt glands activate as needed, providing a mechanism for managing salinity challenges in their diverse aquatic habitats.