Cormorant control reduces damage to island trees

MORRISTOWN — Tree damage on a Morristown island caused by nesting cormorants was reduced by a summer's worth of measures to cut down on the bird's nesting population along the St. Lawrence River.

Approximately 100 cormorants were killed and almost 60 nests were destroyed on American Island, according to James F. Farquhar, state Department of Environmental Conservation wildlife biologist out of Watertown.

"While efforts on American Island did not eliminate tree damage, the level was much reduced this year," Mr. Farquhar said. When cormorants nest, the feces they deposit on the trees can kill them.

This summer also saw a drop in the number of cormorant nests destroyed on the St. Lawrence River and islands of the eastern basin of Lake Ontario, mainly because of a decrease in overall numbers, Mr. Farquhar said.

Last year, more than 1,300 cormorants nests were destroyed on private islands in the American sections of the river and the lake, mainly Gull Island. DEC fisheries technicians, hired seasonally, worked with U.S. Department of Agriculture wildlife services staff during the effort to control the fish-eating cormorant population.

Mr. Farquhar said the control programs accounted for the removal of 609 cormorant nests from Gull Island and 606 taken from private islands on the river. An additional 56 were destroyed using shotguns to "break eggs in nests we could not reach," he said.

He said field technicians reported fewer nests on the river and an overall increase of cormorant numbers on Lake Ontario.

"St. Lawrence River numbers appeared similar; overall nest count was actually down a little. On the lake, local numbers were down slightly. Overall lake numbers were up a bit, mostly due to increases on the western end," Mr. Farquhar said.

While the aim was to remove nests, cormorants were killed during the control program.

"We took 145 in Lake Ontario, fewer than in the past, due to lower overall numbers on our sites," he said. "We took 40 birds on St. Lawrence River islands, not counting American Island."

The wildlife biologist said that some level of the program likely will continue for the foreseeable future.

"On the lake, our efforts are shifting from intensive control towards less intensive maintenance. On the St. Lawrence River, we are really in a maintenance mode, preventing colonization and perpetuation of nesting colonies," Mr. Farquhar said. "Someone once said that cormorant management is like mowing the grass — you have to do it periodically, as needed, to meet goals of habitat protection, reduction of fish predation, etc."

Cormorants reportedly can eat their weight in fish every day and anglers are concerned with their effect on the river and lake fisheries, especially the yellow perch fishery, which is a staple of the birds' diet. A 2003 report by DEC showed that cormorants on just three islands on the St. Lawrence consumed an estimated 23.52 million fish over a three-year period.