Silver maples (what you have), naturally peel their bark as they mature..although judging by the healing going on in the second photo, that almost looks like it's recovering from something else...hopefully someone else chimes in that knows more than I..

With the way the wood curls in, it almost looks like two trees that grew together.

tj

P.S. May be time to move the bird feeder.

What I see is a large, old wound that is healing pretty well. But the bark is different on the callus wood and that is why it is falling off.