This serves 3 purposes:
1) Keeps dogs and predatory animals away from the chickens. No hawk or coyote can get inside. For fool-proof night-time lockdown, they must be put in a coop, of course.
2) The chickens clean all bugs away from the garden. They can be let into the garden area once the plants are mature so that they can take out any bug infestations. They would much rather munch on tasty bugs than peck at a mature plant. Once they get hungry and start molesting my garden, back into the perimeter they go....
3) The double fence (two 5 foot tall fences) completely stops the deer population from getting in and ravaging the plants and tender bark on the younger trees. Deer will jump over a single 5-6 foot tall fence easily, but will never attempt a double fence. If they do, they will be caught inside the perimeter fence and that just means venison for dinner the next night....
Sixteen foot long stock panels (5 feet tall with 4x4 mesh) can be used for the fencing with chicken wire along the bottom to keep the little chicks out of the garden area. The meshed panels support themselves with a simple post every 8 feet and can be used for vining crops such as raspberries and for training apple trees along the panel in the new pruning methodologies (heavy gauge wiring is typically used).
I have enclosed an idea of my garden for your enjoyment (CLICK ON FOR LARGER VIEW):
