Mareca strepera, commonly known as the Gadwall, is native to the Northern Hemisphere. Its geographical distribution includes parts of North America, Europe, Asia, and small regions in North Africa. During the breeding season, Gadwalls are primarily found in the central and northern United States, as well as southern Canada. In Europe, they breed across northern and central parts, extending into parts of Russia and Siberia.

Gadwalls favor habitats such as freshwater wetlands, including marshes, ponds, lakes, and reservoirs, with abundant aquatic vegetation. They thrive in temperate to boreal climates, often choosing habitats that offer both open water for foraging and dense vegetation for nesting.

As primarily herbivorous ducks, Gadwalls feed on a variety of aquatic plants, grasses, and submerged vegetation, but they also consume small invertebrates. They play an essential role in their ecosystem by influencing the growth of aquatic vegetation and serving as prey for predators. Seasonal movements can lead to variations in their habitat preferences, as they migrate south to more temperate regions during winter, where they inhabit coastal estuaries and inland water bodies.