DETROIT A study of more than 30 years of data on bald eagles in Michigan shows the leading causes of death for the iconic national bird are being hit by cars and lead poisoning. Fish and Wildlife Service, Michigan State University and the Michigan Department of Natural Resources. James Sikarskie, a retired professor from Michigan State Universitys College of Veterinary Medicine, was a co-author of the study. Lead poisoning causes damage to the liver and kidneys, and the treatment to draw the toxin out, chelation, is also traumatic on them.Michigan officials said they encourage non-lead ammunition. DNR spokesman Ed Golder said its a hunter preference partly because non-lead ammunition is more expensive.