Mute swans: destructive invaders or scapegoats?© Brian C. Howard
Some environmental and bird conservation groups say the thousands of mute swans now on the East Coast and in the Great Lakes region are invasive intruders that compete with native birds and other wildlife for habitat and food. "They’re big, they’re aggressive, and they can eat a lot of food," says Greg Butcher, director of bird conservation at the National Audubon Society. "We don’t think that’s healthy for the native birds."
Animal rightists don’t agree that mute swans are damaging. "Mute swans are scapegoats for the real environmental polluters," says Michael Markarian, executive vice president of the Humane Society of the United States (HSUS). "These groups are making an arbitrary distinction. They’re saying they like some birds and they dislike others."
Wildlife managers say mute swans are destroying significant amounts of submerged aquatic vegetation and chasing other shorebirds away from their nesting sites. Animal rights advocates say managers haven’t proven conclusively that the birds are responsible for significant damage to aquatic plants. Kathryn Burton, president of Save Our Swans USA, says wildlife officials have overestimated the amount the mute swans eat. She attributes the decline in plants such as eelgrass to pollution, high-speed water traffic and natural cyclic die-offs. "You can’t blame mute swans for everything," she says.
Wildlife officials say they have scientific data to back up their estimates of swan damage to underwater plant life in the Chesapeake Bay area. "While they’re not the primary cause of decline, they are one of the primary obstacles to reestablishing it," says Jonathan McKnight, associate director of habitat conservation at the Maryland Department of Natural Resources.
In March, the U.S. Fish and Wildlife Service published a list of non-native bird species, exempting mute swans from coverage under the Migratory Bird Treaty Act (MBTA). Originally, the act did not distinguish between native and non-native bird species. In 2001, a case brought by animal rights groups resulted in a federal appeals court ruling that mute swans were protected under MBTA. Last year, Congress revised MBTA to exclude non-native birds. "Now, states can manage mute swans at their discretion," says Nicholas Throckmorton, a spokesperson for the U.S. Fish and Wildlife Service.
In Maryland, wildlife officials are following their state’s original plan to reduce the mute swan population by addling eggs and shooting as many as 1,000 of them this spring, though animal activists managed to get the program temporarily put on hold.In April, the Fund for Animals (which merged with HSUS in January) took the dispute back to court, challenging the federal government’s right to remove federal protection for mute swans. The outcome could determine whether mute swans are treated as invaders or become permanent residents on the North American landscape.