American black ducks (Anas rubripes) are medium-sized dabbling ducks found in eastern North America. They are omnivorous birds that eat a variety of plant and animal foods. Understanding what plants American black ducks eat can provide insights into their habitat needs and help guide conservation efforts for this species.
As omnivores, American black ducks have a diverse diet consisting of plant and animal matter. Their diet changes depending on habitat, season, and food availability. American black ducks forage by dabbling in shallow water or grazing in wetland vegetation. Their wide, flat bill is well-adapted for straining food from water or pulling up shoots and leaves. Their diverse diet provides the nutrition and energy needed for migration, breeding, molting, and other life cycle events.
Aquatic Plants
Aquatic plants make up a significant part of the American black duck’s diet. These are plants that grow in or near the shallow wetland habitats where black ducks dabble and feed. Here are some of the key aquatic plants consumed:
- Pondweeds (Potamogeton species) – Abundant pondweeds provide high-energy seeds and vegetation.
- Wigeon grass (Ruppia maritima) – An important food source, especially for wintering black ducks.
- Wild rice (Zizania aquatica) – Black ducks graze on wild rice shoots and consume the nutritious seeds.
- Bur-reeds (Sparganium species) – Shoots, stems, and seeds of bur-reeds are eaten.
- Arrowheads (Sagittaria species) – Provides tubers, seeds, and foliage.
- Duckweeds (Lemna species) – These small floating plants provide cover and forage.
These aquatic plants provide important nutrition for American black ducks. Their high protein content aids growth and development in ducklings. Carbohydrates provide energy for thermoregulation and demanding life cycle events. Some aquatic plants also provide useful cover from predators while ducks are feeding and loafing.
Seeds & Grains
American black ducks supplement their diet with seeds and grains from wetland plants. Key plant seeds consumed include:
- Sedges – Black ducks consume seeds from various sedges (Carex species) that grow in marshes.
- Smartweeds – Seeds of smartweeds (Polygonum species) are eaten when abundant.
- Millets – Seeds from millets and grasses are foraged in wet meadows or agricultural fields.
- Oaks – Acorns from oak trees provide an important source of fats and carbohydrates in fall.
- Maple – They sometimes graze on newly sprouted maple seeds.
Gleaning seeds from wetland vegetation provides American black ducks with a good source of carbohydrates and oils. The variety of seeds they consume aids digestion and provides a range of micronutrients. Their expansive post-breeding dispersal allows black ducks to take advantage of localized seed abundance in wetlands across North America.
Wetland Plants & Greens
American black ducks supplement their diet with various greens, shoots, roots and other vegetation found in wetland habitats. Key wetland plants include:
- Cattails – Shoots, roots, and leaves of cattails are consumed. Provide carbohydrates.
- Bulrushes – Shoots and roots of bulrushes (Scirpus species) are eaten.
- Spikesedges – Underground tubers of spikesedges (Eleocharis species) are dug up.
- Beggarticks – Leaves and seeds of Beggarticks (Bidens species) are eaten.
- Water lilies – Graze on leaves and stems. Provide cover while feeding.
- Arrow arum – Shoots and leaves of Arrow arum (Peltandra virginica) are consumed.
This wide variety of wetland vegetation provides nutrients as well as grit and fiber needed for digestion. Their grazing and dabbling allows American black ducks to exploit the seasonal abundance of wetland plants across their range. The protein and minerals gained prepare them for energetically demanding periods.
Agricultural Crops
American black ducks will fly out to feed in agricultural fields at night or during winter and migration. Key agricultural crops consumed include:
- Corn – Very important source of carbohydrates and calories during winter and migration.
- Wheat – Graze on freshly sprouted winter wheat in early spring.
- Barley, oats – Glean these grains in harvested fields.
- Beans, peas – Important source of protein.
- Potatoes, carrots – Provide nutrients when wetlands are frozen.
These agricultural crops are often eaten from September to March when wetland foods are less available. Corn and wheat in particular provide abundant food energy needed for thermoregulation, migration, and preparing for breeding. Their flexible foraging ability allows American black ducks to exploit seasonal surpluses.
Invertebrates
Animal matter makes up about 15-20% of the American black duck’s diet. They consume a variety of invertebrates including:
- Snails – Important source of protein and calcium for bone and egg development.
- Aquatic insects – Diving beetles, dragonfly larvae, caddisflies, and other aquatic insects are consumed.
- Grasshoppers – Abundant source of protein from summer through fall.
- Crayfish – Provide protein as well as iodine for thyroid function.
- Earthworms – Eat worms in wet fields and mudflats.
- Mussels – May pry open small mussels for protein-rich meat.
These invertebrates provide a good source of protein and micronutrients to compliment the plant-based diet. Aquatic invertebrates are more important for ducklings which require ample protein for rapid growth and development.
Plant Group | Examples | Key Nutrients |
---|---|---|
Aquatic Plants | Pondweeds, Bur-reeds, Duckweeds | Protein, Carbs |
Seeds & Grains | Sedges, Smartweeds, Corn | Carbs, Oils |
Wetland Vegetation | Cattails, Bulrushes, Water Lilies | Protein, Fiber |
Agricultural Crops | Corn, Wheat, Peas | Carbs, Protein |
Seasonal Variation
The composition of the American black duck’s diet changes throughout the year as food availability shifts. Some key seasonal patterns include:
- Spring – Feed heavily on protein-rich aquatic invertebrates and vegetation to regain condition after winter and prepare for breeding.
- Summer – Consume more seeds, grains and vegetation to meet energy needs while molting and rearing ducklings.
- Fall – Build up fat reserves by gorging on abundant seeds and agricultural grains before migration.
- Winter – Rely more on agricultural crops like corn as wetlands freeze over.
Their diverse and opportunistic diet allows American black ducks to adapt to seasonal changes in wetland food availability across their range. This flexibility is key to meeting the unique nutritional and energetic demands they face throughout the year.
Geographic Variation
The specific plants American black ducks consume can also vary across their geographic range. Some notable regional differences include:
- Northeast – More reliance on pondweeds, wild rice, and agricultural grains.
- Southeast – Consume more cypress knees, water lilies, and rice cutgrass.
- Midwest – Corn and sago pondweed are especially important.
- West – Bolboschoenus maritimus is a key food source.
- Coastal – Eelgrass rhizomes, widgeon grass, and mussels are more often eaten.
American black ducks are flexible foragers, able to exploit the diversity of wetland habitats across North America. Their broad diet helps them adapt to regional and seasonal differences in plant food availability throughout their range.
Conclusion
American black ducks have an expansive, plant-dominated diet consisting of aquatic vegetation, seeds, agricultural crops, and other wetland plants. Protein-rich aquatic invertebrates are also consumed. Their diverse diet provides the nutrition needed for their demanding annual cycle. As habitat generalists, American black ducks are able to adapt their diet to take advantage of the variety of food resources available across wetlands in North America throughout the year. Understanding details of their dietary habits provides insights that can guide wetland conservation efforts to preserve food resources critical for maintaining American black duck populations.