Diving ducks, or divers, are a group of waterfowl uniquely adapted to forage beneath the water’s surface, a behavior that separates them from their relatives, the dabbling ducks. While dabblers feed by tipping their bodies in shallow water or grazing on the surface, divers completely submerge to find their food in deeper aquatic environments. Their morphology and behavior are specialized for this underwater lifestyle, allowing them to exploit food sources unavailable to other ducks.
Core Dietary Intake: Invertebrates, Fish, and Plants
The diving duck diet is highly varied, characterized by a greater reliance on animal matter compared to dabbling species. Aquatic invertebrates form the dietary staple for many diver ducks, providing necessary protein and calcium. These invertebrates include small bivalves like clams and mussels, snails, crustaceans such as amphipods, and the larvae of various aquatic insects. Some groups, such as the scaup, consume large quantities of mollusks and crustaceans, particularly during the wintering season when they frequent coastal areas.
Plant matter is also an important component, though its prominence varies by species and season. Certain divers, including the canvasback, specialize in consuming the vegetative parts of aquatic plants, such as the tubers and roots of submerged species like wild celery.
Specialized fish-eaters, like the mergansers, rely on small fish for the majority of their sustenance. They also consume invertebrates, worms, and even small amphibians or mammals when available. The proportions of these food types change based on the season, life stage, and local availability, with females often requiring a high-protein invertebrate diet during the nesting season for egg production.
Physical Adaptations for Underwater Foraging
The diver duck’s body structure is engineered for efficient underwater movement. Their legs are set far back on the body, providing maximum thrust and leverage for propulsion while diving. This rearward placement makes them appear awkward when they walk on land, as they are not balanced for terrestrial movement.
A compact, streamlined body shape minimizes drag and resistance underwater, allowing them to glide efficiently. To aid in submerging, divers compress their feathers against their bodies, squeezing out trapped air to reduce buoyancy. This, combined with a generally higher body density than dabbling ducks, allows them to sink more easily before initiating the dive.
Their feet are large and fully webbed, functioning as powerful paddles for propulsion; some species also have a lobed hind toe. The structure of the bill varies depending on the primary food source. Fish-eating divers possess narrow, serrated bills that allow them to grasp slippery prey underwater, while species that consume mollusks often have a heavy, stiff bill suitable for pulling up hard-shelled prey from the substrate.
Diving Techniques and Habitat Selection
The process of a dive begins with the duck compressing its feathers and then using a powerful thrust of its legs and feet to propel itself beneath the surface. Once submerged, they primarily use their large webbed feet to paddle, often stroking both feet simultaneously. Steering is accomplished through subtle shifts in the position of the head and tail, though some sea ducks may also use their wings for additional propulsion.
Diving duration and depth are directly related to the type of prey and habitat. Most divers forage in relatively shallow water, typically between two and ten feet deep, staying underwater for 10 to 30 seconds at a time. Some sea ducks are accomplished divers, frequently feeding in waters up to 65 feet deep.
The preferred habitat strongly dictates the available diet and foraging strategy. Ducks that feed on immobile prey, such as submerged aquatic vegetation or clams, often surface close to where they dove. In contrast, ducks hunting mobile prey like small fish or crustaceans may surface 50 feet or more from their initial dive point after pursuing their meal. Divers tend to favor the deep, open water of large lakes, reservoirs, and coastal estuaries.