Some bald eagles migrate and some do not. According to the National Audubon Society, whether an eagle moves depends on its age, where it breeds, the local climate and how much prey it can find in winter.
Eagles that breed in the northern interior, north of about 40 degrees north latitude, migrate south between August and January. Juveniles tend to leave earlier and travel farther than adults. Adults that breed south of 40 degrees north are often permanent residents that stay put all year, although their young may disperse or migrate. In spring, northern eagles return to their breeding grounds between January and March, as food becomes available. In the Pacific Northwest and Alaska, many eagle movements line up with salmon runs. Bald eagles migrate alone and during the day. They sometimes join other eagles along the way but do not form flocks. Common routes follow the Pacific and Atlantic coasts, the Mississippi River and the Appalachian Mountains.
Source: National Audubon Society, “Bald Eagle” field guide
Image: Bald eagle in flight, by the U.S. Fish and Wildlife Service, public domain, via Wikimedia Commons.