A diving duck is a type of waterfowl that finds its food by completely submerging its body underwater, distinguishing it from surface-feeding or dabbling ducks. These birds are built to exploit food resources in deeper, more open water environments, such as large lakes, reservoirs, and coastal bays. They have evolved unique physical and physiological traits that enable sustained underwater propulsion and foraging.
Physical Adaptations for Submergence
A diving duck’s anatomy is structured for underwater performance, starting with its powerful legs. Their legs are positioned far back on the body, functioning like a propeller for maximum thrust and steering while submerged. While this placement provides excellent aquatic locomotion, it causes the ducks to walk awkwardly on land.
The body is compact, streamlined, and denser compared to dabbling species, reducing buoyancy and drag in the water. Before a plunge, the bird compresses its feathers to expel trapped air, further lessening the tendency to float. The wings are relatively smaller and more compact, requiring the bird to take a running start across the water’s surface to achieve flight.
Once underwater, the ducks use their large, webbed feet to generate powerful, sustained propulsion. Their dense, layered plumage traps a small amount of air for insulation while remaining highly waterproof. Diving ducks also possess the “diving reflex,” a physiological response that reduces their heart rate and rations oxygen during extended dives.
Foraging Behavior and Diet
Diving ducks initiate a dive with a downward thrust of the head and neck, followed by rapid strokes of their feet. They maintain underwater trajectory and speed through powerful kicking motions from their specialized legs. Steering is accomplished by subtle movements of the head, tail, and sometimes the wings, which act as hydrofoils.
These birds prefer deep, open bodies of water, including deep-water marshes, large inland lakes, and marine coastal areas, where food is inaccessible to surface feeders. A typical foraging dive lasts between 10 and 30 seconds, though some species can remain submerged for over a minute. Most species seek food in the 6-to-10-foot range, but some sea ducks can plunge to depths exceeding 150 feet.
The diet is highly dependent on habitat and season, but it generally includes a greater proportion of animal protein than that of dabblers. They consume a wide variety of aquatic invertebrates, such as mussels, clams, and crayfish, along with small fish and fish eggs. Plant material, including the seeds and vegetative parts of submerged aquatic plants, also forms a significant component of their intake.
Key Groups of Diver Ducks
Diving ducks are classified into several groups, each with specialized foraging niches. The pochards, sometimes called bay ducks, include species such as the Canvasback, Redhead, and Lesser Scaup. Canvasbacks are recognizable by their sloping profile, while scaup often form large flocks, referred to as “rafts,” on open water.
Another group is the sea ducks, which comprise:
- Eiders
- Scoters
- Goldeneyes
- Buffleheads
The Bufflehead is the smallest North American diving duck and is unique for nesting in tree cavities.
Mergansers, often called sawbills, are characterized by a long, thin bill with serrated edges, adapted for catching and holding fish. The Common Merganser and Red-breasted Merganser are frequently seen in both freshwater and marine habitats. Eiders are among the deepest divers, found in cold, northern coastal waters consuming large quantities of shellfish.