Sorry! The correct answer is #3: Eagles become less active, seek protection from the elements, and shiver. While activity can cause muscles to become warm, it also consumes much-needed energy. Micro-climates - think about the needled branches of a pine tree, or a pocket in a limestone bluff - provide some protection from wind and help eagles retain body warmth that would otherwise be lost to open sky. Panting loses heat, but shivering efficiently produces heat at up to five times an eagle's normal rate of heat production.
We've seen eagles bring furry prey in, but they do not use the pelts. While some eagles migrate - bald eagles are partial migrants - not all eagles migrate and they don't fly specifically to NE Florida. The eagles that nest there in November and December are residents.
To learn more about how eagles maximize energy gain and minimize energy loss, read this blog: https://raptorresource.blogspot.com/2015/02/how-do-eagles-stay-warm.html