Great Lakes Article:

Gulls reflect changes in Great Lake pollutants
CBC News Online
Published May 6, 2004

TORONTO - By studying gulls around the Great Lakes, scientists are tracking changes in contaminant levels in wildlife.

For 30 years, the Canadian Wildlife Service has studied gulls, hardy, raucous birds that have been exposed to pollution.

They've found contaminants in gull eggs have fallen by up to 95 per cent over three decades.

"I've noticed that the population of birds are larger than they used to be and noticed not as many eggs broken because of thin egg shells," said Chip Wesleoh, a wildlife biologist with the service.

He said the birds are also more successful at reproducing, but some male gulls have female egg protein in their bloodstream.

The feminization of males existed 30 years ago, but scientists don't know to what extent.

"Gulls feed on fish and we feed on fish and if gulls have PCBs and DDT then we probably have them inside of us," said Wesleoh. The birds are a good starting point to look for any physiological problems.

The researchers have recently discovered a new pollutant, brominated diphenyl ether, or BDE, in eggs. The chemical is used as a flame retardant and resembles a thyroid hormone.