I had not planned to enclose the top of my run; HOWEVER, we have had a bizarre influx of hawks in our area. We live on a river. In years past, we would see a few hawks - a couple a week. Now, we are seeing a couple a day. Also, it appears that many (if not most) of our wild ducks have lost their ducklings. I do not want my new chicks to be here today, gone tomorrow. Any inexpensive recommendations to top off a 18' X 30' run? Thanks!