From Birds and Blooms
For the past several years, woodpeckers have pecked large holes in the siding of our house. Owl decoys don't scare them away. Do you have any other ideas?
To the woodpeckers, your house is just another way to make sound. Thy often drill on houses—or trees, utility poles, antennas, etc—to declare their territory to other woodpeckers. The noise also helps them attract and keep mates. In other words, the tapping is the woodpecker’s song.
There are many ways to prevent woodpeckers from drilling on houses. You can scare them with noise or hang shiny strips of Mylar tinsel, aluminum or metal on your house. I’ve even heard of home owners squirting woodpeckers with water from their garden hose. Another strategy is to cover the area with netting or wire.
It takes persistence, but it should pay off when the woodpeckers move on to find more hospitable territory.
Source: Birds and Blooms