The most comprehensive study on bald eagle mortality in the state of Michigan finds that human activity is the biggest threat to the iconic bird.
Researchers with the U.S. Fish and Wildlife Service, in conjunction with Michigan State University, the Michigan Department of Natural Resources and others, reviewed the cause of death of almost 1,500 eagles.
The leading causes of death: vehicular trauma and lead-poisoning.
Lead author of the study and a fish and wildlife biologist for the U.S. Fish and Wildlife Service Dr. Kendall Simon said lead poisoning comes from eagles ingesting lead from hunter-shot animals and lead sinkers from fisherman.
She said hunters could make an impact by not using lead ammunition.
“That’s a great first step for hunters, if they want to proactively switch from lead to non-lead ammunition. That would be a huge step to not only benefit eagles, but all scavenging species in Michigan.”
Due to human development, ideal habitat along waterways has been taken away from eagles, causing them to settle inland, which causes the bird to need alternative food sources. Food sources include roadkill.
“We recommend for vehicular trauma, states or county departments to not entirely remove carcasses from roadways because it is definitely an important food source for eagles,” Simon said. But to just remove them away from the main thoroughfare or move them to a nearby field.”
Data showed that vehicular trauma related deaths increased in the fall for bald eagles. Lead poisoning deaths increased in the winter and early spring months, when waterways are often covered in ice, causing eagles to resort to eating carcasses of deer that were shot, but not recovered.