"If they have been here for awhile, waterfowl very quickly become unsafe to eat," said David  Allen of the U.S. Fish and Wildlife Service.  "I think hunters should be very careful."

The study released Monday is the latest development in the proposed cleanup of the industrial chemical PCBs, or polychlorinated biphenyls, from sediments of the Fox River, which flows into Green Bay.

Earlier, the Fish and Wildlife Service found that PCBs were contaminating fish in the bay.

"The thing which will probably be surprising is how consistent the findings are," said Allen,  who is managing a federal project to measure PCB damage to natural resources.

"No matter where you take a measurement and no matter what species you measure, you  still find the PCBs. They are everywhere."

Researchers found about 250 species of birds on the bay, making it one of the richest bird habitats in the nation, Allen said.

Twenty-six of those species were intensively studied.  Higher levels of PCBs were found in all 26 species when compared with similar birds further inland, Allen said.

In terns, deformities were found, and the birds' eggs didn't hatch as well, Allen said.  Bald  eagles that nest on the shores of the bay generally produce fewer young than eagles that nest further inland, he said.

As for ducks and geese, "those birds which are newly arrived from Canada have very little level of PCBs and are safe to eat," Allen said.  "But birds which live here all summer have extremely high levels of PCBs and are unsafe to eat."

PCBs were widely used in the making of carbonless paper and other products at paper mills along the Fox until the government banned the chemicals in 1977.  Studies have linked PCBs to cancer, reproductive problems and poor mental development in children and said they are hazardous to aquatic life.

The U.S. Environmental Protection Agency wants a 39-mile portion of the river dredged of the silt from Lake Winnebago downstream to Green Bay.

Seven paper mills were held responsible for dumping thousands of pounds of PCBs into the Fox River. The companies have said they favor a state-run cleanup over federal intervention.  They pledged $7 million two years ago to help clean up the river.

The companies have argued that PCB levels in fish tissue are declining.

Mark Lindley, a spokesman for the paper mills, said the industry had not received a copy of the new bird study and could not comment on it late Monday.

Greg Hill, a supervisor involved in the cleanup for the state Department of Natural  Resources, said the agency also had not received a copy.

The solution to restoring healthy birds to the bay is simple: cleaning up the Fox River so no more PCBs flow into the bay, Allen said.

"Birds will recover on their own if you do nothing, but it will take decades, and in some estimates, centuries," he said.  "If you clean all the PCBs in the river today, it would accelerate how quickly PCBs decline in birds in the bay."