I also have very large pens too with trees in them all covered. Originally I didn't have enough of the good netting to completely cover all of the pens so I bought some cheap crappy netting that an owl went through. It killed some birds. I bought some good netting to replace the crappy netting with and no more issues. After I put the new netting up the owl tried again but got caught. We managed to get it into a cage and a wildlife rescue came and got it.