Sea ducks represent a unique group of waterfowl. While “sea duck” is a common term rather than a specific species, it encompasses various duck species that have adapted to life in marine environments. These birds spend significant portions of their lives in coastal waters, often migrating to northern regions for breeding. Their existence in saltwater habitats highlights their evolutionary specialization.
What Makes a Duck a Sea Duck?
Sea ducks possess a range of specialized adaptations that allow them to thrive in harsh marine conditions. Unlike dabbling ducks that feed on the surface, sea ducks are proficient divers, often propelling themselves underwater using their powerful webbed feet and sometimes even their wings. Their legs are set further back on their bodies compared to other ducks, which enhances their underwater maneuverability but makes them less agile on land. To counteract buoyancy, sea ducks have denser bones and can compress their plumage, reducing the air trapped beneath their feathers.
A key adaptation for marine living is their highly waterproof plumage, which includes a dense layer of down feathers that trap air for insulation against cold water. To manage the high salt intake from their diet of marine invertebrates and from drinking saltwater, sea ducks possess specialized salt glands located in their heads. These glands excrete excess sodium chloride as a concentrated saline solution, typically from the nasal cavity, enabling them to maintain their body’s osmotic balance. Their diets primarily consist of marine organisms such as mollusks, crustaceans, and small fish, which they forage for by diving. Some species, like mergansers, have serrated bills specifically adapted for gripping slippery fish, while eiders and scoters have stouter bills for prying shellfish from rocks.
Notable Sea Duck Species
Eiders are among the largest sea ducks, known for their insulating down feathers, which they use to line their nests. Common Eiders, for example, are large, heavy-bodied ducks with distinctive sloping profiles; males display black and white plumage with green accents on the neck. They primarily feed on shellfish, such as mussels, which they pry from rocks.
Scoters are another group of sea ducks, often recognized by their dark plumage. The Common Scoter, for instance, is a dark-colored sea duck, with males being entirely black and females appearing lighter with pale faces. They frequently form large rafts offshore and are known for their ability to dive deep for mollusks. Surf Scoters, found in North America, have velvety black bodies, white patches on the forehead and nape, and a bright, multi-colored bill.
Long-tailed Ducks are medium-sized sea ducks known for their elongated tail feathers, particularly pronounced in males. These ducks have a complex molt pattern, displaying different plumages throughout the year. They are also known for being highly vocal, with males producing a melodious yodeling call. Long-tailed Ducks are capable of reaching depths of over 60 meters (200 feet) to feed on crustaceans, mollusks, and small fish.