Consider a 10X20 PVC pen that u can move around ur acreage. Mine is similar to the 5x6pen shown in MPC under coop accessories. I made mine from pvc I had around the house and covered half of it with a tarp using shower curtain hooks for shade/protection from rain. We have lots of hawks and bald eagles here. I wouldn't even consider free ranging on our 2 acres even though we have trees & bushes.
That said ur birds and terriers are gorgeeous.

