I'm not sure what this sound is, or why he makes it, but if anyone has any answers, that would be great. He does it most of the night while he's roosting, and then just during the day while he's walking around. Is there any reason for it? I think it sounds sort of like a TV with static, or maybe like a growling. I'm not really sure. I'm hoping from this video, someone can please help. He's about 5-6 months old, if that helps at all.