Brood amalgamation of Trumpeter Swans Cygnus cygnus buccinator

Abstract

We documented post-hatch brood amalgamation in Trumpeter Swans in the northern Rocky Mountains of the United States. During 1987-90, 11.5% of swan broods were involved in amalgamation, and the rate of amalgamation did not vary by year. There were significantly more broods, and a higher density of broods on wetlands where amalgamation occurred than on wetlands where amalgamation did not occur. Possible mechanisms for amalgamation are discussed.