Among the most striking waterfowl of South America, this species is easily recognized by its elegant color pattern and the distinctive whistling calls that inspired many of its common names. Mareca sibilatrix is a medium-sized duck with a sturdy body and graceful appearance. Its head is predominantly white, contrasting with a brilliant iridescent green crown that may appear bluish under certain lighting conditions. The neck and breast display fine gray barring, while the flanks show warm cinnamon tones. The back is dark, and the wings feature extensive white patches that are highly visible both at rest and in flight. The bill is relatively short, bluish in color with a dark tip, and the legs are grayish. Males and females are similar in appearance, although females generally exhibit slightly duller coloration. Juveniles show a less contrasted and more subdued plumage than adults.
Geographic distribution: This species is widely distributed across southern South America. It occurs from central and southern Brazil, Paraguay, and Uruguay through much of Argentina and Chile, including southern Patagonia and Tierra del Fuego. Some populations undertake seasonal movements related to water availability and food resources, while others remain in the same areas throughout the year. Local abundance may fluctuate depending on climatic conditions and wetland water levels.
Habitat: It inhabits a broad variety of continental freshwater environments, including lagoons, marshes, wetlands, reservoirs, slow-flowing rivers, and flooded grasslands. It favors open aquatic habitats with abundant emergent or shoreline vegetation but is also frequently found in human-modified environments such as dams, artificial ponds, and agricultural wetlands. At certain times of the year, it may occur in sheltered coastal habitats, estuaries, and brackish-water environments.
Diet: Its diet is primarily herbivorous and opportunistic, consisting of seeds, shoots, leaves, roots, and a variety of aquatic plant materials. It also consumes small invertebrates such as aquatic insects, mollusks, and crustaceans, particularly during the breeding season when nutritional requirements increase. Most feeding takes place in shallow water, where it grazes, filters, or pecks at available food sources. It may also forage while walking across muddy shorelines or floating vegetation.
Behavior: This is generally a gregarious species, commonly observed in pairs, small groups, or large flocks outside the breeding season. It is active and alert, maintaining frequent vocal communication among flock members. Its clear and melodious whistles are among the most characteristic sounds of the wetlands it inhabits. In flight, it appears agile and direct, with the conspicuous white wing patches serving as an excellent field mark. It often shares wetlands with other ducks and waterbirds, forming mixed-species groups.
Breeding: Breeding generally takes place during spring and summer, although timing may vary according to local environmental conditions. The nest is usually placed on the ground, concealed among dense grasses, marsh vegetation, or shrubs near water. The female prepares a shallow depression lined with dry vegetation and down feathers. Clutches commonly contain between five and ten eggs. Incubation is performed mainly by the female, while the male may remain nearby during part of the breeding period. The ducklings are precocial, leaving the nest shortly after hatching and following their mother to feeding and shelter areas.
Conservation status: Globally, the species is classified as Least Concern (LC) by the International Union for Conservation of Nature because of its extensive range and the absence of evidence indicating population declines severe enough to warrant a higher threat category. Nevertheless, local populations may be affected by wetland loss and degradation, water pollution, drainage of flooded areas, and other human-induced environmental changes. The long-term preservation of healthy wetland ecosystems is essential for maintaining stable populations throughout its range.
Author of this compilation: EcoRegistros – 21/06/2026