Dr. Jeff Levengood, a scientist with the Illinois Natural History Survey, has found that black-crowned night herons living in marshes near Lake Calumet, IL, have the byproduct of DDT in their tissue. The byproduct of DDT, DDE, is found in these birds at a rate of one part per million. Dr. Levengood is the primary author of a paper documenting this contamination, which was published in the December 2007 issue of the Journal of Great Lakes Research.
In the paper, Dr. Levengood suggests that the birds can serve as an "environmental sentinel" for the pollution clean-up efforts in the Lake Calumet area.
For additional information, see the following links: "Bird haven hides traces of poison DDT byproducts found in Lake Calumet marshes" in the May 25, 2008 Chicago Tribune
"Contaminant Exposure and Biomarker Response in Embryos of Black-crowned Night-herons (Nycticorax nycticorax) Nesting near Lake Calumet, Illinois" in volume 33, issue 4 of the Journal of Great Lakes Research.