About Anas fulvigula Ridgway, 1874
Adult mottled ducks (Anas fulvigula) measure 44 to 61 cm (17–24 in) in total length from head to tail. They have a dark body, lighter colored head and neck, orange legs, and dark eyes. Both sexes have a shiny green-blue speculum (wing patch) that does not have a white border, a trait that distinguishes it from the mallard's speculum. Males and females have similar overall appearance, but can be told apart by bill color: the male's bill is bright yellow, while the female's bill ranges from deep to pale orange, and occasionally has black splotches along the edges and near the base. Compared to female mallards, mottled ducks have darker plumage, especially on the tail, and a yellower bill. In flight, the lack of a white border on the speculum is a key identifying difference from mallards. American black ducks are darker than most mottled ducks, and their wing patch is more purple than blue. Mottled ducks share the same behavior and vocalizations as mallards. They feed by dabbling in shallow water and grazing on land. Their diet consists mainly of plants, and also includes some mollusks and aquatic insects. Mottled ducks are fairly common within their limited range, and are year-round residents that do not migrate. Their breeding habitat is brackish and intermediate coastal marshes, but they also use human-developed areas including retaining ponds, water impoundments, and agricultural land during the breeding season. A review of their breeding behavior records that mottled duck nests can be found in pastures, levees, dry cordgrass marsh, cutgrass marsh, spoil banks, and small islands. Sex-specific measurements are as follows: Males: Length 19.7–22.5 in (50–57 cm), Weight 30.9–43.8 oz (880–1,240 g), Wingspan 32.7–34.3 in (83–87 cm); Females: Length 18.5–21.0 in (47–53 cm), Weight 24.7–40.6 oz (700–1,150 g), Wingspan 31.5–327.2 in (80–831 cm).
