Two to three year old birds begin their courtship on the wintering grounds. The courtship ritual includes synchronized swimming, bill dipping, blowing in the water, and dueting. The young couples may not nest for another year or two. They prefer sizable bodies of water with an ample supply of food plants, dense surrounding vegetation for privacy, and plenty of room for take-offs. Nest building begins soon after arrival, with the refurbishing of last year's nest or the selection of a new site.
Trumpeters often build on top of muskrat houses or beaver lodges.
They uproot surrounding vegetation clearing a moat for visibility and building up the center until the final product measures up to 2.5 m across and rises 40 cm above the water line. She incubates for 33-35 days, leaving the nest only for short periods to forage. The male swims nearby, guarding against predators. Fluffy pale gray down covers the newly hatched cygnets. They leave the nest after a day or two to begin to feed themselves.