The loon is a highly specialized migratory aquatic bird, recognizable as an icon of the northern wilderness and its expansive freshwater lakes. These powerful swimmers spend the breeding season across the northern United States and Canada, inhabiting quiet, undisturbed waters. Their annual return signals the start of summer, and their haunting presence is linked to the solitude of boreal forests. The loon’s existence is centered on the water, having developed unique physical and behavioral adaptations for diving and fishing.
Identifying Physical Traits
The loon belongs to the genus Gavia. The most widely known species, the Common Loon (Gavia immer), displays striking black and white breeding plumage. This summer attire features an iridescent black head and neck, a prominent white “necklace,” and a back covered in a checkerboard pattern of black and white spots. This distinctive pattern helps camouflage the bird against the dappled light of the water’s surface.
The loon’s body is torpedo-like, built for underwater speed and maneuverability. Adult Common Loons are large, generally weighing between 7 and 15 pounds and measuring up to three feet in length. They possess dense, solid bones, which, unlike the hollow bones of most flying birds, reduce buoyancy and allow them to sink quickly and dive effectively.
Their large, webbed feet are set far back on the body, functioning like powerful propellers for rapid underwater propulsion. This rearward placement makes them extremely clumsy on land, forcing them to shuffle awkwardly on their chests. Consequently, loons only come ashore for mating and nesting purposes, spending nearly all their time on the water.
The Unique World of Loon Vocalizations
The loon’s complex vocal array is a defining characteristic of their presence on northern lakes, serving as a sophisticated system of communication. Four distinct calls are used to convey specific information within their territory and to other loons.
The Wail is a long, mournful sound often compared to the howl of a wolf. It is primarily used for long-distance communication between mated pairs or to signal a desire for contact, especially when a loon is separated from its mate or chick.
The Tremolo is a quavering, high-pitched call that sounds like maniacal laughter. It functions primarily as an alarm or distress signal when loons feel threatened by a predator or approaching boat. It is the only call they can make while in flight.
The Yodel is a loud, aggressive call used exclusively by the male to defend his territory during confrontations with intruding loons. Each male’s yodel is individually recognizable, acting as an acoustic signature that conveys information about the male’s size and his motivation.
The Hoot is a short, soft call used for close-range communication between family members. This intimate call is typically exchanged between parents and their chicks or between pair members to maintain contact as they forage near one another.
Aquatic Lifestyle and Breeding Habits
The loon’s entire annual cycle revolves around its ability to hunt and navigate in water, making it a master of the underwater environment. They are pursuit predators, using their powerful legs to drive themselves through the water at high speed to catch fish, which constitute up to 80% of their diet.
Loons can perform deep dives, sometimes reaching depths of 200 feet, and can remain submerged for up to five minutes while hunting. They swallow most of their prey underwater, using their sharp, dagger-like bills and specialized rearward-pointing projections on their tongue to secure slippery fish.
Nesting occurs in the spring on freshwater lakes large enough to provide a long “runway” of open water, which they need to gain enough speed for takeoff. The nest is a simple scrape or mound of vegetation built right at the water’s edge, often on a small island or secluded shoreline for protection.
The female typically lays one or two olive-brown eggs, and both parents share incubation duties for about 28 days. Once hatched, the dark, downy chicks can swim almost immediately. They are often seen riding on their parents’ backs for warmth, rest, and protection from predators. The family remains on the breeding lake until the water begins to freeze, which triggers their migration to coastal ocean waters for the winter.
Species Diversity and Conservation Status
The loon family, Gaviidae, includes five distinct species globally, such as the Red-throated Loon, Pacific Loon, and Yellow-billed Loon. The Common Loon is the species most often encountered in North American lakes. While classified as a species of least concern globally, loon populations are vulnerable to several human-related threats, particularly on their breeding grounds.
One significant issue is mercury contamination, which bioaccumulates in the loon as it consumes fish higher up the aquatic food chain. High mercury levels act as a neurotoxin, causing lethargy in adults and reducing their ability to forage and care for their young, lowering reproductive success.
Loons are also highly susceptible to lead poisoning from ingesting fishing tackle, such as lead sinkers and jigs, which they mistake for small stones needed for digestion. Lead toxicosis is a leading cause of adult loon mortality in some regions, prompting efforts to promote the use of non-toxic alternatives. Habitat loss, acid rain, and recreational disturbance also pose ongoing challenges, requiring continued monitoring and conservation efforts.