Aythya affinis, commonly known as the Lesser Scaup, is native to North America. It is primarily found in Canada and the northern United States during the breeding season. In winter, the species migrates to the southern United States, Central America, and the Caribbean.

The Lesser Scaup typically inhabits lowland freshwater environments such as lakes, ponds, and slow-moving rivers. During migration and in winter, they are also found in coastal estuaries and sheltered bays. The climate in their breeding regions is generally temperate to subarctic, while their winter habitats can vary from temperate to subtropical conditions.

Lesser Scaup are diving ducks, often feeding on aquatic invertebrates, plant material, and small fish. They play a role in controlling invertebrate populations within their aquatic habitats. Their preference for open water bodies provides them with the space needed for diving pursuits and reduces predation risks.