OK. I think I have figured out what that noise is. It starts every night at about 9:00 p.m. and goes on until after midnight or until after I fall asleep, whichever comes first. Two weeks ago I would have guessed it was a wild pig wandering across my back porch, but then the noise seemed to take up residence every night. I started asking nature-lovers what it could be. I started imitating its high-pitched sound and someone suggested that it could be a screech owl.
Two nights ago I arrived home late and heard a tall tree emitting this high-pitched sound. Aha! That means it's not a wild hog. Huge sigh of relief.
I love birds. I have hummingbird feeders and a seed feeder. I was hoping for painted buntings to be regular visitors. But instead I got a screech owl whose favorite perch is right outside my windows. Nocturnal creature that he is, I don't even get the pleasure of seeing him. I only get to let him sing me to sleep. I think I need to pray more.