The Black-bellied Whistling Duck ( Dendrocygna autumnalis ) is a medium-sized, gregarious waterfowl species found throughout the Americas. Known for its distinctive appearance and vocalizations, this duck exhibits unique feeding behaviors and dietary preferences that contribute to its ecological role. This article delves into the intricate details of the Black-bellied Whistling Duck's diet and foraging habits, shedding light on its food sources, foraging strategies, and adaptations.
Habitat and Distribution
Black-bellied Whistling Ducks inhabit freshwater swamps, marshes, and coastal lagoons. They favor habitats with dense vegetation and surrounded by tree thickets, partially due to their nests usually being built in tree cavities. This helped to earn them the nickname tree ducks. These ducks can be found in shallow freshwater ponds or lakes, often those containing water hyacinth, water lilies, and cattails.
Their range consists of large portions of South America and along the coast of Central America. Today, in the United States, Black-bellied whistling-ducks are mostly found along the Gulf Coast, the southern portion of the Mississippi River, and the Florida Panhandle. In South Carolina they are found primarily along the coast, mostly in the southern portion of the state. They have been reported as far inland as Aiken county and as far north as Georgetown county.
General Diet
Black-bellied Whistling Ducks are primarily herbivorous, with plant matter constituting over 90% of their diet. They are vegetarians and will use agricultural grains, especially rice and corn. These ducks are known to feed in both shallow water and on land. What makes them unique is that they often feed at night, leaving roosts at sunset to fly to foraging areas.
They search among fields and shallow freshwater areas for plants, seeds, grains, small insects and invertebrates to eat.
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Specific Food Sources
The diet of Black-bellied Whistling Ducks is diverse and includes a variety of plant species and agricultural crops. Some of their primary food sources are:
- Seeds and Grains: Seeds of various emergent and aquatic plants. Also feeds on cultivated grains, including rice, sorghum, and corn. They feed mostly on seeds of various grasses, also of smartweed and other plants.
- Aquatic Plants: Smartweed, grasses, swamp timothy, amaranth, sedges, bindweed, and nightshade. They forage in fields, lawns, and shallow, freshwater ponds that often contain water hyacinth, water lilies, and cattails.
- Agricultural Crops: They also eat many agricultural crops including sorghum, millet, corn, rice, and wheat. Individuals are attracted to areas where corn and rice are grown and can cause damage to crops.
While their diet mainly consists of plant material, they also consume a smaller amount of aquatic animals such as snails, insects, and spiders. Only a small part of their diet consists of animal matter, like leeches, snails and beetles.
Foraging Behavior
Black-bellied Whistling Ducks exhibit unique foraging behaviors, influenced by their habitat and dietary preferences. These behaviors include:
- Nocturnal Feeding: They typically forage at night, leaving roosts at sunset to fly to foraging areas.
- Terrestrial and Aquatic Foraging: They feed in fields or by dabbling in shallow ponds. When foraging, often in dry fields, also in irrigated land. In shallow water may wade to reach emergent plants, or may dabble at surface or tip up to reach under water.
- Gregarious Feeding: They are gregarious year-round, forming flocks of up to 1,000 birds. Flocks come to harvested fields to feed on waste grain, also to prairies and overgrown pastures.
- Adaptability: The species has become well adapted to feeding in agricultural fields and, as a result, large flocks can be seen foraging in pastures and open fields.
Nesting and Diet
Black-bellied Whistling Ducks nest in thickets or stands of mesquite, hackberry, willow, live oak, and other trees. Nest site usually in tree cavity or broken-off stub, 4-20' above ground or water. Tree nests on land usually close to water, but can be up to 1/4 mile from it. Also frequently nests on ground, in dense low growth near water. Many now use nest boxes; have also nested in chimneys, barns. Cavity nests are bare or with a few wood chips, but ground nests are woven of grasses and weeds.
Usually nests in tree hollows where a limb has broken or the trunk has rotted away. They also use nest boxes and sometimes nest on the ground. Both sexes help select the nest site. Whether nesting in natural cavities or nest boxes, Black-bellied Whistling-Ducks typically don’t build a nest; they lay their eggs directly on whatever debris has collected there. Cavity openings range from 5-12 inches across. When nesting on the ground, they make a scrape or a shallow bowl of grasses, with thick vegetation overhead, such as willow, mesquite, or cactus.
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The diet of Black-bellied Whistling Ducks influences their reproductive success, as they breed during their first year of life. Incubation is shared by both sexes and normally ranges from 25-30 days. If one of the adults is lost during incubation the other typically abandons the nest. Some black-bellied whistling ducks will renest if their first nests are destroyed. Most nest failures are caused by desertion as a result of egg predation by raccoons or rat snakes.
Conservation Status
Partners in Flight estimates the global breeding population at 1 million and rates them 8 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. North American population has greatly increased since 1950s. In Texas and eastern Mexico, providing of nest boxes probably helped this expansion. In Arizona (where most nests apparently are on ground), species was very rare before 1949, has since become a fairly common nesting bird.
Black-bellied Whistling Duck numbers appear to be stable to increasing throughout their range, but the species is not subject to large-scale surveys. Breeding Bird Survey data in the United States suggests populations are increasing, perhaps by as much as 8% annually. Harvest is believed to be very low, estimated to be below 20,000 annually, with the most harvest occurring in Texas and Louisiana.
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