What is bald headed bird and has a brown body and is a scavenger?

The eagle.

Five letters: e a g l e

An eagle will hunt and fish, but it will take the role of a scavenger if carrion is available for the taking.

Sounds like the bald eagle you describe here. Bald eagle's diet consists of around 70% fish, but will take ducks and other waterfowl, also small mammals on occasion. They will scavenge dead animals as well, as will most raptors, especially the Buteo hawks, including the red tailed, red shouldered, and broad winged hawks.