Scientists hoping cormorant control project will succeed

FOUR BROTHERS ISLANDS, N.Y.—When thousands of cormorants descended on nearby Young Island, within a few years they had killed all its trees, turning it to an eerie landscape of nettles, thistle and bird droppings.

Now environmental groups and state agencies monitoring Lake Champlain are hoping to cut back on a population of birds that has boomed since the pesticide DDT, which had decimated cormorants and other birds, was banned.

Cormorants are blamed by anglers for eating too many fish, and by wildlife biologists for squeezing out too many other bird species.

Now scientists are trying to reduce their population by coating their eggs in spring with vegetable oil, which prevents them from hatching. They're trying to use the birth control technique enough so that it reduces the birds' population without persuading the cormorants to move elsewhere, taking their destructive habits with them.

On a visit last week to the Four Brothers Islands, David Capen, a University of Vermont scientist, and Tom Berry, Lake Champlain program director for the Adirondack chapter of the Nature Conservancy, checked to see how well the birth control technique had worked this spring.

The Conservancy, which owns the Four Brothers Islands off the New York shore of a lake shared by New York, Vermont and Quebec, had resisted calls to limit cormorant populations, but relented in part to save habitat important to great blue herons and other water nesting birds.

The problem has grown acute. Some 30,000 cormorants are sharing the islands' 16 acres this summer.

Now the trick, the men say, is to reduce the birds' reproductive success but not so much that they merely move to another part of the lake.

"You can't manage one island in isolation," Berry said. "Cormorants move around. We need a lake-wide plan."

Vermont and New York wildlife officials had tried destroying the birds' nests and killing cormorants, but the birds merely moved elsewhere on the lake. The Nature Conservancy said it wouldn't take steps to limit the birds until the states developed a lake-wide plan.

Now that has happened, and officials are hoping a new era of cooperation will result in greater success.

"It has taken the Nature Conservancy a long time to explore options for managing cormorants," said John Austin, interim wildlife director at the Vermont Fish and Wildlife Department. "What they are doing on Four Brothers now has opened the door for us to work together."

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Information from: The Burlington Free Press, http://www.burlingtonfreepress.com