Long-tailed ducks are generalists that consume a large variety of prey. Animal foods that are commonly eaten by long-tailed ducks include: crustaceans, mollusks, marine invertebrates, small fish, fish eggs, freshwater insects and insect larvae. Some plant material that is also consumed includes: algae, grasses, seeds and fruits in the tundra biome. Studies show that mature adults prefer marine animals. Specifically, they tend to eat blue muscles, Idotea baltica (isopods), northern lacuanas, and Amphipoda crustaceans which yield higher energy per gram of live mass than other available prey.
Mature adults typically forage diurnally, about 80% of the day, during the winter months. Usually, individuals dive with submerged times ranging from 25 to 60 s and pick epibenthos within 100 m of the shore. Since long-tailed ducks are relatively small when compared to their marine Anatidae counterparts, they must maintain a particular diet for physiological and thermoregulatory purposes.
Long-tailed ducks have several physical characteristics that make them successful predators. First, they have chisel-shaped bills that curve at the tip which would help grab epibenthos prey from their substrates. Second, long-tailed ducks have smaller bills, allowing them to efficiently pick small, motile crustaceans. Finally, the body shape and structure of mature adults aids in diving and agility in water, giving individuals a powerful advantage over their primarily cursorial or sessile prey.
Animal Foods: fish; eggs; insects; mollusks; terrestrial worms; aquatic crustaceans; echinoderms; other marine invertebrates
Plant Foods: leaves; seeds, grains, and nuts; fruit; algae
Primary Diet: carnivore (Eats other marine invertebrates)