Whistling ducks (Dendrocygna) are waterfowl known for their long legs, upright stance, and clear whistling calls. They are sometimes called tree ducks because some species perch in trees. These birds inhabit tropical and subtropical wetlands across the globe, from the Americas to Africa and Asia. Their diet focuses overwhelmingly on plant life found in and around water bodies.
The Predominantly Plant-Based Diet
The diet of whistling ducks is almost entirely herbivorous. Their feeding habits center on consuming various seeds, especially those from aquatic and marsh plants like sedges, grasses, knotgrass, and smartweed. Cultivated grains form a substantial part of their diet, particularly near human agriculture. They readily consume grains such as rice, corn, sorghum, and wheat, often foraging in flooded fields. They also ingest vegetative parts of plants, including bulbs, tubers, and stems.
Animal matter makes up a small portion of the overall adult diet, typically less than 10%. This limited intake includes small aquatic invertebrates like snails, leeches, aquatic worms, and insects. This consumption is usually incidental to their primary foraging for plant seeds and roots.
Specialized Feeding Behaviors
Whistling ducks are highly adept at grazing on land. They exhibit a goose-like behavior, walking in pastures or fields to clip grasses and low vegetation. Their long legs facilitate this terrestrial movement, unlike many other duck species.
In aquatic environments, they employ several techniques. These include dabbling and tipping up in shallow water to reach submerged materials, and diving to access roots and tubers deeper underwater. Some species are filter-feeders, using their bills to strain fine mud and water to extract small seeds and invertebrates.
A distinguishing characteristic is their tendency toward nocturnal feeding. They frequently leave their daytime roosts near dusk and fly to foraging areas, such as rice paddies or flooded fields. This nocturnal activity allows them to exploit food resources when human disturbance is minimal.
Dietary Changes Across Seasons and Life Stages
During the breeding season, females preparing for egg-laying and incubation often increase their protein consumption. This dietary shift involves consuming a higher proportion of invertebrates. This provides the necessary protein and calcium for successful egg production.
The diet of young ducklings is distinct from that of adults. While they are capable of feeding themselves immediately after hatching, they rely more heavily on invertebrates for rapid growth. They transition almost entirely to an adult herbivorous diet after this developmental period.
Seasonal shifts in food availability also influence their choices, especially for migratory populations. They rely on abundant carbohydrate-rich resources like seeds and cultivated grains to build energy reserves for migration and wintering. Their opportunistic nature allows them to shift foraging locations to agricultural fields when natural wetland seeds become scarce or covered by ice.