Cool facts from the Cornell website: "Bufflehead breed near ponds and lakes in boreal forest and aspen parkland of Canada and Alaska, with isolated populations in the western United States. The Bufflehead’s breeding range is limited by the distribution of Northern Flickers, which are their main source of nesting cavities. Bufflehead are North America’s smallest diving duck; they benefit by using old flicker nests that larger ducks such as goldeneyes and mergansers cannot fit into. In winter they occur mainly near the coast (although they can be found in smaller numbers inland). They use shallow, sheltered coves, harbors, estuaries, or beaches, avoiding open coastlines. Inland, they use ponds, lakes, impoundments, or bays along slow-moving rivers. During spring migration they spend time on major rivers or valley lakes, often in the first spots to become free of ice."
Here are some pics from the Aquarium Pond at Fort Fisher in 2018.