It nests in remote northern freshwater wetlands, with emergent vegetation, that are free from disturbance. Nests are large heaps of vegetation placed well away from shore. Only one pair usually occupy a marsh because of intensive interspecific aggression towards other swans during the nesting season. Pairs usually mate for life. The breeding season extends from late May to mid-September.
Family groups remain together throughout the fall migration and winter.
Trumpeter swans return to nesting marshes year after year, but are sensitive to disturbance and will abandon nests and nesting marshes if harassed. In winter, trumpeter swans are gregarious and flocks of over 100 birds are regularly found at favoured wintering sites. They frequent agricultural fields, rivers, estuaries, mudflats, sloughs and shallow lakes. This species is an uncommon and locally distributed breeding bird in northern B.C. Known breeding lakes are in extreme northern B.C., in the Peace River area and in the central part of the province. Although known sites are few, this swan likely breeds in scattered localities across the northern parts of the province.