Fulvous Whistling-Duck Life History

Habitat

Fulvous Whistling-Ducks frequent freshwater wetlands, usually with water less than 20 inches deep. In the United States, they use impounded, flooded rice fields and similar habitats such as flooded pastures and agricultural fields. They often nest in the rice fields where they forage. Before and after nesting, Fulvous Whistling-Ducks occupy a greater variety of habitats. Newly arrived migrants in spring sometimes show up in brackish or saltwater marshes, but most occupy freshwater marshes and slow-moving rivers with emergent vegetation. Flocks in Texas and Louisiana preparing to migrate southward concentrate in freshwater wetlands near the coast. In Florida, some Fulvous Whistling-Ducks remain year-round in rice fields, but many occupy freshwater marshes extensively after the nesting season, especially during winter. They often roost in forested areas next to marshes or rivers (a former name for this species was Fulvous Tree Duck). During the late fall, the migratory western Gulf populations move into lagoon systems in eastern Mexico, where they become flightless for a time as they molt (replacing their flight feathers). Wintering birds there inhabit many kinds of wetlands, from freshwater marshes and ponds to flooded savannas, mangrove swamps, and riparian forests.

Food

Fulvous Whistling-Ducks eat mostly invertebrates and the seeds of aquatic plants. They forage by swimming or wading in shallow water and dabbling, tipping up, or diving to reach food with the bill. Where insects are present on vegetation or on the water’s surface, they sometimes glean or pick them with the bill. Both this species and Black-bellied Whistling-Ducks graze on vegetation, but Fulvous Whistling-Ducks are more often filter-feeders, foraging by touch and straining fine mud through the bill to extract seeds and invertebrates. In rice-growing areas, where some farmers consider them pests, these whistling-ducks feed mostly in fields that have been seeded when flooded rather than when dry. In addition to rice seed, they eat green algae and seeds of wheat, knotgrass, switchgrasses, sedges (many species, including beakrush and fringe-rush), jungle-rice, bahiagrasses, darnel ryegrass, reed canary grass, signalgrass, watershield, cape blue waterlily, blue mudplantain, knotweed, robust marshwort, spearwort, Colombian waxweed, slender fimbry, and sea ragwood. Invertebrates such as earthworms, midges, water beetles, dragonfly larvae, snails, and small mollusks make up a small part of the diet for adults, perhaps a larger portion for ducklings.

Nesting

Nest Placement

Male and female select the nest site together, flying over and landing in several spots before choosing the site, usually in weedy rice fields, in stands of reeds, grasses, or rushes, or on floating vegetation.

Nest Description

Both male and female arrange a platform of vegetation by bending stalks, eventually forming a bowl shape as they add dead marsh grasses. Most nests also have ramps for access to water. As the nest decays and sinks, or becomes flooded by changes in water levels, adults add new material. Nests average about 14 inches across, with the interior bowl 9.7 inches across and 4.3 inches deep.

Nesting Facts

Behavior

Fulvous Whistling-Ducks court one another rather briefly, facing each other and dipping the bill, and this behavior often serves as a prelude to mating. After mating, pairs usually perform a display side by side, nodding the head, paddling with the feet, raising the breast, and extending the outside wing (that is, the wing not next to their mate). Multiple males often chase a single female through the air. Like other whistling-duck species, Fulvous is probably monogamous, with pairs staying together year-round, similar to geese and swans but unlike most ducks (family Anatidae). However, there is some evidence that males mate with multiple females. For most of the year, Fulvous Whistling-Ducks forage, rest, and roost in flocks. In mid-April, pairs begin nesting and spend much of their time away from flocks. They do not establish or defend a territory but do defend the nest, and both male and female share incubation and chick-rearing duties, unlike in most duck species. Individuals in conflict raise their crest feathers and move their heads, and this sometimes escalates to biting, kicking, and beating with wings. Like many other waterfowl species, Fulvous Whistling-Ducks are often brood parasites—they lay their eggs in other ducks’ nests. Conflicts between ducks appear to arise when the nest owner defends its nest against parasitism. After the young fledge, Fulvous Whistling-Ducks gather in flocks that can number in the hundreds or over a thousand. In Texas and Louisiana, these flocks migrate southward into Mexico, where they molt, becoming flightless for several weeks as they replace their flight feathers. Some may molt before migrating southward. They remain gregarious throughout the winter and into spring, migrating northward in flocks.

Conservation

According to the North American Breeding Bird Survey, Fulvous Whistling-Duck populations remained relatively stable overall or increased slightly between 1966 and 2015, though a Southern California population declined and then vanished during that period, for unknown reasons. Partners in Flight estimates the global breeding population of this worldwide-distributed species at 1.4 million and rates the species a 9 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. In some parts of the range, agricultural pesticides have caused sharp declines in populations of this species. Fulvous Whistling-Ducks are hunted worldwide; the impacts of hunting on its numbers are not known, as this is one of the least studied of waterfowl species. The species responds rapidly to changing water levels, moving sometimes far out of its typical range in search of satisfactory conditions for foraging and breeding. Worldwide, the degradation of floodplain habitats by drainage, channelization, and development pose the greatest conservation threat to the species.

Credits

Hohman, William L. and Sarah A. Lee. (2001). Fulvous Whistling-Duck (Dendrocygna bicolor), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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