This is damage caused by sapsuckers, woodpeckers that drill holes through the bark of trees to reach the sap in the cambium layer.  When they return to the same tree, they often drill the old holes bigger and drill so many holes that they eventually girdle and kill the tree.  Even with little drilling, their holes give openings to insects which can further damage the tree.  You can discourage them by wrapping the tree trunk in burlap or hardware cloth.  Some people hang aluminum foil strips or old CD's that move in the breeze to try to scare them off.  If they have already done a lot of damage to one tree, you might want to leave the hopeless one and wrap other trees nearby so that they don't attack those.