Bob S. said:

That's why the lower strand is at 6 inches - to keep the smaller
critters out. Haven't found anything to keep the squirrels out of the
corn though.

A fence with a small mesh that's topped with a couple of electric wires
will keep out fox squirrels. Small heavy-duty paper bags will ward off
birds. I've notice the local squirrels will always go over or under a fence
in preference to going through it -- even the small red squirrels which
you'd think should be able to slip through.

(Advice from experience: don't cheap out on the paper bags.)
--
Pat in Plymouth MI ('someplace.net' is comcast)

Any technology distinguishable from magic is insufficiently advanced.
(attributed to Don Marti)