For the last few weeks, every night I hear this high pitch whistling coming from just about everywhere in the woods it seems and it's constant When it first started, I half ass thought it was my neighbor out whistling for his pup, which sounds just like him. I then kept thinking it was some kind of owl, but I don't think so. I just came in from checking the fire pit & these birds or whatever seemed to be everywhere ( not really, but close ). The only way to describe it is as you'd be out walking your dog & you'd whistle to get its attention or so. Never heard this before until a few weeks ago as stated.