Controlling swan's nest egg

State wildlife biologists take back bay from invasive and destructive mute swan

April 19, 2007|By Candus Thomson | Candus Thomson,Sun Reporter

It starts with aerial photos then switches to hip boots on the ground and boats in the water.

Little by little, state wildlife biologists are reclaiming the Chesapeake Bay from mute swans. Where two years ago, more than 3,600 of the graceful white birds filled the bay and tributaries, fewer than 1,500 remain.

Just as there is no denying the beauty of the swans, there is no denying their destructiveness. The swans eat precious underwater plants that provide sanctuary for fish and crabs and food for wintering waterfowl, such as canvasback ducks.

"It's good we're getting this species under control," says Dr. David Curson, director of bird conservation for Audubon Maryland-DC. "It's painful to see a beautiful bird killed. But it's even more painful to see a beautiful ecosystem damaged."

John Grandy, head of the waterfowl section of the Humane Society of the United States, says the group is "disappointed" that having killed 2,200 swans, the Department of Natural Resources is continuing the hunt. The group's leadership met about three weeks ago with DNR Secretary John Griffin to urge him to stop the killing.

"Let's let bygones be bygones," Grandy says. "It's the people of Maryland who love these birds, not just the Humane Society. Let's step back from the precipice and assess the situation."

Other states with mute swan problems and tribal leaders of the Ottawa Nation in Michigan are watching Maryland's program with keen interest. Success here in the courtroom and in the field might lead to the acceleration of eradication programs.

"This is a success story," says Perry Plumart, director of conservation advocacy for the American Bird Conservancy. "I hope that Maryland has provided a road map for how to deal with a destructive species, to show that this can be done and done responsibly."

These days at the Maryland Department of Natural Resources, success is measured nest by nest, bird by bird. That means shooting adult birds and preventing eggs from hatching.

On the edge of a marsh in northern Anne Arundel County, with the Key Bridge in the background, Jonathan McKnight pushes through black muck and six-foot-high reeds that crackle like corn flakes underfoot. An aerial photo has brought the biologist to this spot.

"Here's mom. Here's dad. I hope," says McKnight, pointing out bright dots on the photo. "But you can spend a lot of time looking for a white bucket."

Suddenly, ahead is a cup of dried grass holding seven eggs slightly larger than a man's fist. Beyond the nest, paddling in the brackish water, are two angry, hissing parents.

"If they charge, raise your arms and make yourself larger," says McKnight, who is armed only with a squirt bottle of vegetable oil and his paperwork.

The nest is one of 66 identified in the counties adjacent to the bay's western shore. Baywide, the swans like the Eastern Shore's Talbot County best, perhaps because that was their original point of entry on the bay.

It takes moments for McKnight, the head of the habitat conservation team at the Department of Natural Resources, to slip on a pair of surgical gloves and cover each egg in an oily sheen.

Addling, as it is called, suffocates the embryo. Adult birds will continue to sit on the eggs until breeding season is over. Smashing the shells only triggers another breeding cycle.

Biologists hope to treat more than 80 percent of the approximately 200 known nests this year. But addling alone isn't the answer. Mute swans can live for 20 to 25 years. Each year from the time she's about 3, the female lays an average of six eggs. About half of the baby birds make it to adulthood and old age.

Sharpshooters kill the adults when they are near state land. The best time is usually after the birds moult and are flightless.

The bulk of the money to pay for the program comes from hunting license fees.

McKnight has dealt with every kind of invasive animal and plant, from tree-destroying beetles to the orange-toothed nutria, the bane of marshes from Louisiana to Delaware.

In some ways, the nutria and mute swan are similar. Both were brought to this country and released. In the case of the mute swan, five birds - two females and three males - acquired in the 1950s by a Talbot County landowner escaped from his estate in 1962. By 1999, the population had boomed to 3,900 birds.

Both species can be controlled and both destroy the habitat on which they depend.

"The populations grow and grow and grow until the ecosystem can no longer sustain them. The system crashes and the populations crash, but not before they adversely alter everything in their paths," he says.

DNR managers recall a time in the late-1980s when a flock of about 700 mute swans moved into the Tar Bay area of Dorchester County and destroyed the nesting grounds of least terns and black skimmers, both on the state Threatened and Endangered Species List. The populations of both species went into steep decline.

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