The birds are protected by the state of Illinois from harm. In other words, it's against the law to kill the birds. Sapsuckers will peck horizontal and vertical rows of holes in the trunk and upper branches of the trees.
Sapsuckers create the holes and feed on sap.
They may occasionally feed on insects foraging at the exposed site. Birds will continue to come back to the same trees during migration and peck in the same areas. Insects and disease organisms can enter the tree at the point of sapsucker injury, creating further problems for the plant. Severe and repeated injury can kill parts of or the entire tree. Wrap damaged areas of trees with a loose, coarse material such as burlap to prevent pecking and feeding.