The Cinnamon Teal is a small dabbling duck with a Pan-American distribution. Four subspecies are found in South and Central America, but relatively little is known about the ecology and status of these populations. A fifth subspecies, A. c. septentrionalium, breeds primarily in the Great Basin and western intermountain regions of the United States and winters mainly on coastal marshes and interior wetlands in Mexico. Unlike most North American dabbling ducks, the Cinnamon Teal rarely breeds in the midcontinent prairie-parkland region.
This duck inhabits mostly freshwater or brackish wetlands, including the highly alkaline waters of the Great Basin. Large flocks are uncommon most of the year, but during migration small groups of fewer than 30 individuals often mix with other ducks.
Cinnamon Teal are seasonally monogamous, with most pairs forming before arriving on breeding areas. Females lay 4 to 16 eggs in a well-concealed nest near water in rushes, sedges, and grasses, or sometimes over water in dense bulrushes or cattails. Males remain with their mates until late incubation, and guard females and sometimes sites within wetlands near the nest. After breeding, molting males form small flocks on nearby wetlands or make molt migrations to large marshes with abundant emergent vegetation. Females perform all brood-rearing duties, and usually remain with their young through fledging. Cinnamon Teal begin fall migration earlier than most other North American ducks. Males and unsuccessful breeding females begin southward migration in late summer; most successful females and young birds follow in early autumn.
An omnivorous species, the Cinnamon Teal feeds primarily by dabbling or tipping up in shallow water. Social feeding, in which groups of birds follow each other, dabbling in the water stirred up by the bird in front, occurs throughout the year. Seeds are common in the diet in all seasons and provide a high-energy food source. To meet the protein costs associated with egg production, females increase their consumption of aquatic insects, snails, and zooplankton from spring migration through laying.
Accurate continental population estimates are unavailable for Cinnamon Teal because most birds reside outside regions where extensive breeding and wintering population surveys are conducted. Available data suggest a population size of 260,000 to 300,000 for A. c. septentrionalium, making the Cinnamon Teal one of the least abundant dabbling ducks in North America. Populations currently appear to be stable throughout most of the North American breeding range. Even less is known about the status of South American populations.
Because of its limited range and early fall migration, the Cinnamon Teal is not as heavily harvested in the United States as are most other North American ducks; harvest in Mexico and the neotropics also appears to be light. The availability and quality of wetlands and surrounding upland nesting habitats in the arid West may provide the most important limitation on North American populations. Nest loss to predators can be substantial and limits local recruitment in some areas. Competition with the closely related Blue-winged Teal (Anas discors) may limit further expansion of the North American breeding range of Cinnamon Teal.