Rescued from near extinction, trumpeters breeding in the Greater Yellowstone Ecosystem, including Red Rock Lakes, have grown in number from a low of only 69 birds in 1932, to a success of more than 500 in recent years. These birds are joined each winter by an additional 2000 trumpeters from Canada to form the Rocky Mountain Population of trumpeter swans. These largest of all North American waterfowl measure up to 4 feet, weigh between 20-30 pounds, and have a wingspan of up to 8 feet. The swans must remain near open water to obtain their preferred diet of aquatic plants. They also feed occasionally on grain, seeds, freshwater invertebrates, snails and worms.
Winter is a sociable time for trumpeter swans, but in late winter the swan families drift apart.
The subadult birds form loose flocks, the migrant birds leave for their summer nesting grounds in Canada, and other pairs return to their nearby nesting territories. After spring mating, the pair builds a nest. They may select a new site or refurbish their old one. Favorite sites are on muskrat houses or in broad beds of marsh plants. The swans uproot plants in a large ring and build in the center, leaving plenty of open water all around for good visibility.