A little-studied, diminutive, tropical relative of the Ruddy Duck (Oxyura jamaicensis), the Masked Duck inhabits ponds, small lakes, and other wetlands covered with emergent vegetation from northern Argentina north through South and Central America (east of the Andes) to southern Texas. As with other members of the tribe Oxyurini, the Masked Duck has elongated and pointed tail feathers with stiffened shafts. It is distinguished from other stifftails by its large white wing-patch. Grebelike and secretive in its behavior, the species is infrequently observed, usually as it slips into dense reeds or below water. Often only the tip of its tail and head are visible, as it sinks noiselessly beneath the surface.
The Masked Duck has a long breeding season—nests are found from October until August. The nest is a deep cup usually built near water, sometimes roofed over (basketball-like), containing 4 to 8 eggs. Males are believed to play a minor role in rearing the young. Masked Duck numbers increase following wet cycles that create new wetlands with emergent vegetation. Population biology is poorly understood as populations are difficult to monitor though standardized surveys. Even so, the Masked Duck is hunted in many areas, though hunting is not well regulated and enforcement of existing regulations is typically lacking. Despite its small population in Texas (estimated at 3,800), the species is legally hunted.
Johnsgard and Carbonell's (1) treatise on the stiff-tailed ducks, the most thorough treatment to date of this group, emphasizes how little is known of the Masked Duck compared to other stiff-tailed ducks. Even details on breeding biology and behavior from captive populations are lacking. Informed conservation of this species will depend on filling these gaps in knowledge.