I thought that too but didn’t want to say it He has one silkie hen his age and there are more younger then him. There is also two bantam Cochin girls with him.
Now that I'm done laughing, What about maybe a piece of dried grass or bedding material, something of that nature stuck in his feathers in that area or in his vent?
I checked him over last night and this morning and can’t find anything I posted another thread with the video and @sourland mentioned that it could be ummm “self satisfaction” that has me laughing even more!