Mottled Duck Life History

Habitat

Mottled Ducks use fresh and brackish wetlands for resting, feeding, and nesting. Most select water 6 inches deep or less, in places where there is an abundance of emergent vegetation, including grasses, bulrush, rice cutgrass, and bulltongue. Like many waterfowl, they respond quickly to changes in their environment, moving into temporary wetlands caused by heavy rains or altered water levels such as flooding for rice cultivation. In Florida, the species makes use of many small urban and suburban wetlands, even drainage ditches along busy highways. When molting their flight feathers, Mottled Ducks often gather in large numbers in flooded agricultural fields, whereas during the dry season in the Gulf Coast states, normally from late winter to early spring, they occur in permanent wetlands. Birds in the more westerly population are less often found in suburban settings, favoring rice fields, tidal wetlands of river deltas, oxbow lakes (resacas), prairie ponds, and coastal lagoons.

Food

Mottled Ducks consume a variety of plant and animal matter, which varies greatly by region and season. Common plants taken include the seeds and shoots of many grasses, wild millet, smartweed, spikerush, paspalum, sea purslane, wigeon grass, and bulrush. They also eat cultivated rice, which forms an important part of the fall and winter diet in the western part of the species’ range. Mottled Ducks meticulously strip grass and rice seeds by rapidly opening and closing the bill along the length of the seedhead. Invertebrate prey include snails, crayfish, beetles, amphipods (zooplankton), dragonflies, and midges. Small fish are also eaten. Breeding females consume mostly invertebrates, as do ducklings.

Nesting

Nest Placement

Pairs seek nesting sites by flying low over habitat. Females select the nest site, which is usually not far from water, often at the base of a shrub. The nest itself is typically on the ground or on vegetation less than 3 feet from ground level. Sites vary greatly and include pastures, fields, artificial and natural islands, dredge spoil sites, cordgrass marshes, floating mats of marsh vegetation, hedgerows, road medians, gravel mining pits, pine savannas, citrus groves, sugarcane fields, and scrub oak or shrub-scrub communities.

Nest Description

A circular, bowl-shaped depression in grass, often beneath dense overhanging vegetation. The female constructs the nest and adds grass litter, shredded grass, and down from her breast to the interior, resulting in a well-formed bowl. Few nests have been measured; available measurements are: outside diameter 10.5 inches, inside diameter 6 inches, bowl depth 1.5–3.5 inches, and wall thickness 3 inches.

Nesting Facts

Behavior

Mottled Ducks feed by picking items from the water’s surface or just below it, often tipping the tail skyward as they submerge their heads and bills to reach food below the water’s surface. Compared to other species of ducks, Mottled Ducks form pairs early, mostly in November. Breeding starts in January and continues into July; it usually peaks in March through May. Courtship displays, which can occur in groups larger than 2, are very similar to those of the Mallard, with a great range of stylized movements and sounds involving shaking the head, raising or dipping the head or tail, preening behind the wing, as well as a variety of grunts, burping sounds, and whistles. At first glance these displays may make the ducks seem merely restless, but watch carefully and you’ll see that the motions are directed at other ducks, often prospective mates. Once paired, conflict is infrequent; the most common signs of aggression include opening the bill or chasing a rival either on the water or in the air. Mottled Ducks are seasonally monogamous, with the pair bond usually ending before the ducklings have hatched. In rare cases males assist females with brood-rearing, though not with incubation. After breeding, adults gather in small flocks and molt their flight feathers. Postbreeding autumn and winter flocks can be sizable where food is abundant, though generally not as large as flocks of closely related species such as Mallard.

Conservation

Mottled Duck declined by an estimated 3.1% per year between 1966 and 2015, resulting in a cumulative decline of 78% over that period, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 460,000. Its Continental Concern Score is 17 out of 20 and the species is on the Red Watch List, Partners in Flight’s highest level of conservation concern. Numbers fluctuate widely in response to periodic drought conditions. Wetland drainage in Florida, degradation of coastal marshes by saltwater intrusion and erosion in Louisiana and Texas, and urban development throughout the range pose serious conservation challenges. Mottled Ducks are most imperiled by hybridization with introduced Mallards. The problem is most pronounced in Florida, where 10% of the population is estimated to have Mallard genetic material. The U.S. Fish and Wild Service closely monitors duck populations and hunter activity. In recent years between 20,000 and 50,000 Mottled Ducks have been taken by hunters each year.

Credits

Bielefeld, Ronald R., Michael G. Brasher, T. E. Moorman and P. N. Gray. (2010). Mottled Duck (Anas fulvigula), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Leukering, T., and B. Pranty. (2016). Mottled Duck hybridization. eBird, Cornell Lab of Ornithology, Ithaca, NY. https://ebird.org/content/ebird/wp-content/uploads/sites/55/eBird_Muddled_Ducks.pdf.

Raftovich, R. V., S. C. Chandler, and K. K. Fleming. (2017). Migratory bird hunting activity during the 2015-16 and 2016-17 hunting seasons. U.S. Fish and Wildlife Service, Laurel, MD, USA.

Robbins, M. B., P. McKenzie, and B. Jacobs. (2010). A review of Mottled Duck (Anas fulvigula) reports in the North American interior, with comments on historical records of dark Anas ducks. North American Birds 64:518–522.  .

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

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