I live near an 80 acre lake in California with a number of swans: Mutes, Trumpeters, and Blacks, all pinioned. A black pair has started a nest, and the Trumpeters are harassing it. The swans seemed to get along pretty well until a pair of Trumpeters were brought in (now a family of 6).

What is the best course of action? Should we just let nature take its course? Should we try to manage the swan population? Can we fence off the Black's breeding area to protect it from the Trumpeters?