GRAND ISLE, Vt. (AP) – Tests are being done on about 130 of Lake Champlain’s double-breasted cormorants to try to determine what killed them this summer.

John Gobeille of the Vermont Fish and Wildlife Department said he’s awaiting results of autopsies being conducted by the New York Department of Environmental Conservation the large, fish-eating birds.

Sick and dead cormorants showed up around Young Island off the west shore of Grand Isle and the Four Brothers islands on the New York side of the lake in late July and August.

“We found dead birds on the shore and some birds on the water that couldn’t fly or dive very well,” Gobeille said. “It looked kind of odd.”

Young Island is home to one of the largest breeding colonies of cormorants on Lake Champlain. Biologists coated eggs in nests with vegetable oil in the spring to control the crowded population.

Gobeille said it’s unlikely the spring population control efforts caused adult birds to fall ill in the summer.

“My gut feeling tells me that if those eggs weren’t oiled and we had more young birds out there, we would have seen even more sick and dead birds,” said University of Vermont professor David Capen, who studies the lake’s cormorants.

Young Island is about three acres, and there were 1,250 cormorant nests on it this year, Capen said.

Capen said given the concentration of cormorants at the nesting sites, a disease outbreak was not surprising.

A similar situation struck Lake Champlain in 1990, when hundreds of gulls mysteriously died.

“This is reminiscent of that die-off of gulls,” said John Hall, spokesman of the Fish and Wildlife Department, “and nobody ever found a pathogen responsible for that.”

Biologists were initially concerned the cormorants might have been afflicted by a number of diseases that can be transmitted to domestic poultry. Gobeille said those diseases have not been ruled out.

AP-ES-09-21-03 0847EDT