On Friday, Erika and I birded locally. We flushed this Bald Eagle as we drove around a corner on the north edge of the Carleton College Arboretum along Little Canada Road. The eagle briefly perched atop a nearby pine, but then flew away.
"That would have made a good blog entry," remarked Erika. "Not without a photograph." I replied. About 20 minutes later, we returned to the same spot. We found the eagle perched in a large oak and I was able to take one photograph before the bird again flew.
Bald Eagles require four years to obtain their striking adult plumage. During these years, the eagles continually molt, and so continually change their appearance. According to the description is the Peterson Field Guide Series, Hawks, our bird is probably a second-year bird. This book is a decent field guide to birds of prey and can be obtained through the accompanying link at bargain prices. (Two volumes by Brian Wheeler may be better, Raptors of Western and Eastern North America, but they are expensive. Minnesota is covered in the Western volume.)
The eagle was feeding on an opossum carcass. I assume the opossum was road-kill and that the eagle was scavenging. A cursory search of the literature finds no mention of Bald Eagles consuming opossums. Eagles are primarily fish-eaters, but are known to take a wide variety of prey when fish are not available. Arthur C. Bent, in his monumental masterpiece Life Histories of North American Birds of Prey, wrote, "As eagles do not disdain carrion, they may often be seen...feeding on the carcasses of any animals they can find.." This 26-volume set of books is now somewhat dated, but still contains a wealth of information. The books were first published by the Smithsonian and then reissued as Dover reprints. Prices for these books vary greatly, so some research is advised if you are interested in obtaining them.
If you are interested in up-to-date life histories of birds, the American Ornithologists' Union'sBirds of North America is now a continually evolving, on-line resource. Subscriptions to the series are pricey, but free to AOU members! Some libraries have copies of the print version of Birds of North America, but they do not appear to be available through Amazon.