Herons persist in Chicago wetlands despite exposure to banned chemicals

Loafing black-crowned night-herons near Lake Calumet, Illinois, with coking plant in background. Click here for more information.

Herons nesting in the wetlands of southeast Chicago are still being exposed to chemicals banned in the U.S. in the 1970s, a research team reports. The chemicals do not appear to be affecting the birds’ reproductive success, however.

The findings appear in the current issue of the Journal of Great Lakes Research.

University of Illinois veterinary biosciences scientist Jeff Levengood led the study. Levengood, a wildlife toxicologist at the Illinois Natural History Survey, said that chemicals banned 30 years ago for their deleterious effects on wildlife are still showing up in the offspring of black-crowned night-herons in a Chicago wetland.

The researchers found PCBs and DDE in the eggs of night-herons nesting in the wetlands abutting Lake Calumet, in southeast Chicago. The Lake Calumet wetlands are surrounded by industrial developments along Lake Michigan near the Illinois-Indiana border.

The research team included scientists from the U.S. Geological Survey, the Illinois Waste Management and Research Center, and Purdue and Duke universities.

PCBs (polychlorinated biphenyls) were commonly used in electrical transformers and other industrial applications until they were banned in 1977 because of their toxicity in the environment.

DDE is a metabolic by-product of DDT (dichlorodiphenyltrichloroethane), a pesticide banned in 1972 because it was observed to kill or disrupt the reproduction of birds and other wildlife. The DDT ban is believed to have reversed the dramatic decline in the American bald eagle and the peregrine falcon in the continental U.S.

The Lake Calumet birds appear to be picking up the contamination primarily from Lake Michigan by means of an invasive fish, the alewife.