The masked duck (Nomonyx dominicus) is a tiny stiff-tailed duck ranging through the tropical Americas. They are found from Mexico to South America and also in the Caribbean. Primarily not migratory, masked ducks are reported as very uncommon vagrants in the southernmost United States, along the Mexican border and in Florida. As of 2000, the conservation status for masked ducks in Texas is 3,800 birds. On April 1, 1962, it was recorded from Lowndes County, Georgia, where it was photographed by Alexander Wetmore.
The Masked Duck is a rare resident in Puerto Rico (Oberle 2018, Raffaele and others 1998) and a rare visitor in Vieques (Gemmill 2015). The atlas fieldwork yielded a total of 20 records within 11 hexagons or 2 percent of the 479 total hexagons (see map). Of the 11 hexagons where this species was found, breeding met the atlas definition of confirmed in 18 percent (two) of the hexagons, probable in 9 percent (one), and possible in 73 percent (eight) (see map). This species inhabits freshwater swamps and canals with plenty of fl oating vegetation, as well as rice fields (Raffaele and others 1998), brackish water ponds, and lagoons (Oberle 2018).
Previously published reports indicate that the Masked Duck breeds from May to August and nests on swamp vegetation near or over the water (Raffaele and others 1998). Atlas results show that the Masked Duck breeding season extends throughout the year, but the most records were reported in June (see chart). Results show that the Masked Duck mostly breeds within the Masked Duck distribution. The map shows the highest breeding code by hexagon and overlaying the ecological life zones in Puerto Rico. Note: percentages may not total 100 due to rounding. 33Masked Duck/Pato Dominicosubtropical moist (73 percent of the hexagons) and subtropical dry forest life zones (27 percent of the hexagons) (see table and map).
The Masked Duck population is suspected to be declining owing to over-hunting and other human pressure but is listed by the IUCN as a species of least concern (BirdLife International 2016). The Puerto Rican population is composed of around 50 pairs and is under pressure from illegal hunting and habitat degradation associated with human activities (J.A. Salguero-Faría, personal observation 2009). In Puerto Rico, the Masked Duck is listed as endangered (PRDNER 2016) and has a protected habitat in land of 15 percent or 39 km2 of the total area covered by the hexagons where evidence of breeding was found for this species (264 km2).