To many, swans are a picture of beauty and grace — but to others, they’re miscreants hell-bent on environmental destruction. In Connecticut, mute swans — considered an invasive species — can eat eight pounds of shoreline plants per day and, in the process, uproot an additional 20 pounds of vegetation. Their gluttony can disrupt ecosystems, displacing crabs, oysters, and native birds. Conservationists, including the state Audubon Society, are so concerned about the swans’ impact that they’re kickstarting a campaign to reduce the state’s swan population. But if animal-rights activists have their way, the birds won’t have a swan song anytime soon.