how do I keep woodpeckers from damaging my cedar?

Answer 1

If there is a wood pecker in your Cedar, or your House, Garage, Maple Tree etc...
Then the problem is not the wood pecker, the wood pecker is helping to solve the problem.
Wood Peckers ONLY peck at INSECT INFESTED wood.
So you all really had a problem before the Woodpecker came to feed on the insects that have bored your tree.
It is the same for wood houses, barns, telephone poles, and other species of trees.
FIRST, come the really harmful bugs boring into the wood.
THEN come the woodpecker drilling them out and eating them!!!!
You need to either treat the tree for insects or cut it down and disinfect the yard and start again.