My suggestion would be to put up a game camera and see what is around. GHO's can be quite relentless. I had one plaguing my birds. It killed some birds so I moved the birds to another coop and pen and put a camera up and the owl came back. I have netting covering my pens but ran short and bought some crappy netting I thought would probably work but the owl went right through it. I replaced the section with more of the crappy netting because that was all I had at the time and the owl would go through it. I bought some good heavy duty netting like I have over the rest of the pens and the owl tried but got stuck. We managed to get it into a cage and a wildlife rescue came and got it. I have posted these pictures before.
