Loons are iconic aquatic birds known for their distinctive calls and powerful swimming. They are migratory, traveling considerable distances between breeding and wintering habitats each year.
Confirming the Seasonal Journey
Migration is a fundamental aspect of the loon’s life cycle, driven by environmental changes that directly impact their survival. Loons leave summer territories to find suitable conditions for colder months.
The necessity to migrate stems from the freezing of northern lakes, which eliminates their primary food sources and access to open water. This annual relocation ensures year-round access to food and suitable habitats.
The When and Where of Their Travels
Loon migration typically begins in late autumn (late August to November) as northern lakes start to freeze. They embark on southbound journeys to warmer coastal waters or large unfrozen inland lakes. The return migration northward to breeding grounds occurs in spring, generally between March and June, with peak activity in April and May.
Their breeding grounds are primarily freshwater lakes across Canada, the northern United States, Greenland, and Iceland. These lakes, often nestled in northern forests, provide clear water for foraging and secluded nesting areas. For winter, common loons disperse to coastal marine waters along the Atlantic, Pacific, and Gulf of Mexico coasts, or to large southern lakes and inland reservoirs. For instance, loons from the Great Lakes region may winter in the Gulf of Mexico, while those from western Canada head to the Pacific coast. Some Maine loons winter along the state’s coast, while others travel further south to areas like New Jersey or Maryland.
The Driving Forces Behind Migration
The primary reason loons migrate is the availability of open water and food sources. Northern freshwater lakes, their breeding habitat, freeze in winter, making it impossible to access the fish that constitute most of their diet. This forces them to seek ice-free waters where they can continue to forage.
Loons possess dense bones and rear-set legs, making them excellent divers but requiring a long “runway” on water to become airborne. Frozen lakes prevent flight, making open water crucial for foraging and mobility. During winter, their diet shifts from freshwater fish to marine fish, crustaceans, and other aquatic invertebrates found in coastal environments. Specialized salt glands above their eyes excrete excess salt from saltwater prey, enabling adaptation to marine environments.
Breeding cycles also play a role, as northern lakes offer favorable conditions for raising young during summer. Abundant food and fewer predators in these remote areas provide a suitable environment for nesting and chick development. After breeding, adults typically migrate first, sometimes congregating in large groups on staging areas to feed and rest before continuing their journey.
Diversity in Loon Migration Patterns
All five species within the Gaviidae family are migratory, though their patterns vary significantly in distance and specific routes. For example, the Common Loon (Gavia immer) exhibits a wide range of migratory distances; some individuals travel over 3,000 miles, while others move less than 100 miles between breeding and wintering sites.
Pacific Loons (Gavia pacifica) are medium-distance migrants that breed in Arctic tundra lakes and typically winter along the Pacific coast of North America, extending as far south as Baja California, or along the Pacific coast of Asia. These loons migrate in large flocks, a behavior less common in other loon species. The Red-throated Loon (Gavia stellata), the smallest loon species, breeds farther north in the High Arctic. Its populations migrate predominantly along coastlines, with some Alaskan populations wintering in East Asia and others along the Pacific coast of North America. Unlike other loons, the Red-throated Loon can take flight from water more readily, sometimes without a long running start.
Juvenile loons have distinct migration patterns, often remaining on wintering grounds for two to five years before returning to breeding lakes. Adult loons frequently display high site fidelity, returning to the same breeding lakes and wintering areas annually.