Having raised and kept gamebirds for over 10 yrs. I have encountered every varmit known to Nebraska trying to get in these pens. Mink are some of the worst.
I agree, keeping the varmits out is a challenge.
The best way is to trench down and bury tin (such as roofing material type) 8-10 inches below the ground, around the perimeter. The trenching must be done before your posts are set so that your tin will be tight against your posts.
You can use 2x4's ran horizontally at the top of the tin-fastened to your posts and your tin can be screwed directly to the 2x4's.
Your netting can also be fastened to the 2x4's.
The tin, if 3 foot widths, will be out of the ground roughly 2 feet. Therefore if you want 6 foot sidewalls you can get by with 4 ft wide material.
By putting the tin around the bottom I think it helps that the varmits cannot see in. Used corrigated roof tin works well and the nail holes do not hurt anything. It is very inexpensive if you can find it. Farm sales or demolition crews are your best bet. Also, electric fence both at the ground and on top of the 2x4s where your netting starts has eliminated 99% of our varmit problems
Good luck with your venture.
