Toxic chemicals blown from distant sites are disrupting the life cycle of birds on the Great Lakes, and the plight of the water fowl has worsened dramatically in recent years, according to research released recently by environmentalists.

"In a broad sense, these chemicals are eliminating the diversity in the Great Lakes," said James P. Ludwig, a consulting ecologist from Bay City, Mich., at a news conference Tuesday. "We have a few species, but the elegance is gone."Ludwig surveyed thousands of bird eggs and hatchlings in the northern lakes and found sharp increases in deformities such as malformed hips, club feet, eye abnormalities and body organs attached outside the birds at birth.

To demonstrate the effects of pollution, the researchers displayed at the news conference a live cormorant with a twisted beak. The bird, which was found on Naubinway Island, Mich., in northern Lake Michigan, may eventually be placed in a petting zoo.

A 1986-88 survey of water bird eggs in the upper Great Lakes region found deformities in Caspian terns occurring 31 times more frequently than in the late 1960s and early 1970s, Ludwig said.

Even low levels of contamination produced effects in the Great Lakes food chain, Ludwig said.

His research included birds nesting in highly contaminated areas, such as Saginaw Bay in eastern Michigan.

Many contaminants are blown into the lakes from many hundreds of miles away, an ecologist said in describing research last year on Isle Royal, Mich., an island in Lake Superior.

Deborah Swackhammer, an ecologist with the University of Minnesota, studied fish in Siskiwit Lake on the island and found concentrations of the toxic chemical polychlorinated biphenyl.

The PCB could only have reached the lake from the air, since the lake's level is above that of surrounding Lake Superior, she said.

"Not only is every fish in the Great Lakes contaminated by chemicals to some extent, but anything that consumes those fish is also contaminated to some extent," including people, she said.

The research was released as part of a lobbying effort by the Sierra Club.