Woodpeckers drilling holes
I need some information to help determine the exact situation. The picid species birds (woodpeckers, flickers, and sapsuckers) will peck on trees for different reasons.
If it is a woodpecker species and it is successfully hunting under the bark for insects infesting the tree, then the tree is in serious trouble due to the insect damage. Insects feeding under the bark of trees is often fatal to the tree.
If it is a woodpecker or flicker is digging out a nest in the tree, that is also not a good sign for the tree as they usually select ones that have rotting heartwood to make the job easier. The tree could have suffered physical damage in the past and the inside could be weak with decay.
If it is being attacked by a sapsucker, they make a vertical column pattern of holes just through the bark to collect the sap that oozes out for food. Other bird species will also feed on the oozing sap. Migrating humming birds follow the sapsuckers migration north in the spring, as they depend on the sap for food because there are few or no flowers to feed on in the early season in the Rocky Mountain West.
Lastly, flickers will "drum" on trees to mark their territories. Cornell has excellent information on birds of all types and also woodpecker Family in particular. http://www.birds.cornell.edu/wp_about/biology.html
Homeowners have reported some success deterring woodpeckers with windsocks, pinwheels, helium balloons (shiny, bright Mylar balloons are especially effective), strips of aluminum foil, or reflective tape. Woodpeckers are protected by law and shouldn't be killed for following their