Discourage the bird with a garden hose by shooting a jet of water at the bird, or by banging pots and pans together or by making some other sudden loud noises. Tether helium filled balloons at the base of the wall with the balloons floating against the problem area. Hand aluminum pie plates or aluminum strips from the eves across the problem area. Screen off the problem area to exclude woodpecker access. For further information, contact a local US Department of Agriculture Animal Damage Control office or Cooperative Extension Office for more information on these and other wildlife problems.
Birds can see their reflection in a window.
During the breeding season, when the birds are most territorial, they view the reflection as another bird intruding on their territory, and try to chase it away. Most species do not recognize the reflection as their own self. Many species of birds engage in this activity. The best way to discourage this behavior is to place a non-reflective material in front of the window on the outside to prevent the reflection. This is only a temporary behavior that will cease when the breeding season in over.